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\ 


Mechanical Drafting 


/V 

HBy 

H. W. MILLER, M. E. 

Head of the Department of General Engineering 

In the University of Illinois 
Urbana, Illinois 


Drawing 




The Manual Arts Press 
Peoria, Illinois 




% 


T353 

.VA637 


Copyright, 1912 
By 

H. W. Miller and R. K. Steward 


©Q.A328787 

2-Cq ( 










fo 


( 


P R E FACE 

In presenting such a radical treatment of mechanical draft¬ 
ing, both as to arrangement and selection of material, a few 
Iwords of explanation may not be amiss. The author is de- 
fcidedly opposed to giving in a college course in mechanical 
drafting any work of a purely abstract geometrical nature. 
Most students have gotten clear conceptions of the geometri¬ 
cal figures in the high school, and to attempt to teach the use 
of instruments in the drafting of such figures is across waste 
of the student’s time in the already too short college course. 
Long continued trials have definitely proven that the student 
can just as well, and perhaps better, be taught the use of in¬ 
struments on work that will at the same time have intellectual 
value. 

In the usual text on drawing the subject is presented in 
the old order of logically progressive chapters; one chapter 
bn one subject, another on a different subject, and so on. 
This has always made it extremely difficult to design a satis¬ 
factory course of drafting problems in which the instructor 
las not had to do an excessive amount of lecturing. If a 
student is to get a thing and keep it, he must be made to 
iig it out himself, within reasonable limitations. Lecturing 
isimply deducts so much from the time when the student is 
pelf-active. 

With these ideas in mind the author has planned a very 
lexible course and written a text to suit the course. The 
:ourse is divided into distinctly logical steps, and each suc- 
:essive step is made a separate Mock" 4 of work to be finished 






before the next is begun. All of the information needed by 
the student in performing the work of block No. i is com¬ 
piled into Lesson i, and no more. All additional information 
needed for block No. 2 is given in Lesson 2, and so on. Illus¬ 
trations are included for everything that can be illustrated, for 
the student’s visual memory seems to be better than his word 
memory. 

In using this set of lessons the author has discontinued 
lecturing entirely. When a class is ready for the next block 
of work, the corresponding lesson is assigned; the students 
are required to recite on the subject matter, quizzes are given, 
and freehand sketches on the blackboard illustrating all points 
are called for. Successive trials have shown that the students 
thus retain about twice as much knowledge as before under 
the lecturing plan. 

A glance thru the text will show that it has been made as 
practical as possible. Drafting is not so much a theoretical 
subject; it is intended to be used and should be practical. 
Furthermoie, the author has kept in mind the fact that this 
is an age of intense competition, and that a draftsman should 
never draw a piece, of any machine until it has been decided 
on what machine or by what means each surface can be most 
rapidly and cheaply finished. If a certain surface can be 
machined more cheaply on a milling machine than on a shaper 
or planer, then bosses and ribs should not be so placed as to 
prevent milling machine work. To assist in giving the stu¬ 
dent this practical training, illustrations of all the standard 
machines are given, with tools and accessories, so that he may 
gradually learn to couple his drafting with shop operations. 

H. W. Miller. 

Urbana, Illinois, July, 1912. 


2 


CONTENTS 


PAGE 


Lesson 1—Use of Instruments; Offhand lettering. 5 

Lesson 2—Use of Instrument"; Mechanical Block Letters .... 24 

Lesson 3—Construction of Name Plates and Working Drawing 

Titles. 35 

Lesson 4—O thographic Projection; Sectioning; Use of Instru¬ 
ments; Dimensioning; Shop Terms; Conven¬ 
tional Lines; Tracing Cloth; Scales, Rules, Ltc. 43 

Lesson 5—Standard Bolt Threads; Scales; Shop Terms . 79 

Lesson 6 Shop Terms; Sectioning; Standard Threads. 97 

Lesson 7—U. S. Standard Bolts and Screws; Keys and Keyways; 

Conventional Breaks; Bolt Tables . . .. .. 109 

Lesson 8—Assembly Drawing; Detail Drawings; Gate, Globe and 

Check Valves; Pipe Connections .. ... 125 

Lesson 9—Isometric Projection; Shades and Shadows in Isomet¬ 
ric Projection .145 

Lesson 10—Oblique Projection; Conversion of Iron Ores into 

Commercial Iron and Steel . 161 

Lesson 11—Machine Sketching .. ... 178 

Lesson 12—One Point Perspective; The Lllipse. 182 

Lesson 13—Photographic Reproduction, Blueprinting, Ktc. . 196 

Reference Tables. 204 


3 












Fig. 2 


4 














MECHANICAL DRAFTING 


LESSON 1 

USE OF INSTRUMENTS 

DRAWING-BOARD 

(1) Construction. Drawing-boards are made of 
either poplar or white pine, the .right and left edges, Fig. 
1 , being reinforced by cleats of some harder wood. These 
cleats serve both as stiffeners and as runners for the easy 
sliding of the T-square. The better grades of small 
boards are reinforced on the back by two battens, Fig. 2 , 
and ordinarily, have inserted in their right and left edges 
a wearing strip of either hard maple or celluloid, instead 
of the cleats of Fig. 1 . It will be noticed in Fig. 2 that 
the right and left edges of the second class of board 
are broken at intervals by saw cuts which prevent the 
inserted strip of hard wood from expanding and split¬ 
ting the wood. 

Use. The two sides of the type of board shown in 
Fig. 1 have very definite uses if the board is to be kept 
in shape for good drafting. The one side for drafting 
only, the other for any necessary rough work, trimming 
paper, etc. Never trim paper on the drafting side. 

PAPER 

( 2 ) Quality. A novice cannot obtain good work 
from poor material, hence it is imperative that the begin¬ 
ner in drawing use the best quality of paper obtainable. 
A heavy, hard surface paper of the quality of Keuffel & 
Esser’s Normal, or E. Dietzgen’s Napoleon is recom¬ 
mended. 


5 


6 


MECHANICAL DRAFTING. 


~-lw 

N 



Fig. 3 


Edge of sheat 


o| 




Border 

I 0 

1 

1 

_ Q 1 * 



— Q 1 " ^ 

1 

1 

1 

1 

2 u 1 

> 

h 


1 

“P 


1 


1 

1 

1 

1 

1 


s -i 

u 

i 

loi 

t 


1 

1 

L 

o| 




A-V-D'icK.R.-E P 


Fig. 4 





































USE OE instruments. 


7 


Position of paper on board. In tacking the paper to 
the board, Fig. 3, keep the sheet well toward the top and 
to the left; about two and one-half inches from the upper 
and left edges. This should be done in order that the 
draftsman may work to advantage on the bottom of the 
sheet, and that it may not be necessary to work to any 
great extent on the end of the T-sqnare blade, which 
cannot be prevented from springing slightly. 

Tacking sheet. Place upper left corner of sheet in 
approximately correct position and tack to the board, 
Fig. 3, placing tacks close to the corners of the paper. 
Then after lining up the upper edge with the upper edge 
of the T-square blade, stretch sheet and tack upper right 
corner. The lower edges may be tacked down in any 
order; or, after some experience, may be left nntacked, 
as these tacks have a tendency to interfere with the 
T-square and triangles. 

BORDER LINES 

(3) The border lines as well as all other construc¬ 
tion work done by the draftsman should be placed in by 
measurements from center lines and not from the edges 
of the sheet. In the case of the border lines, the meas¬ 
urements are made from the horizontal and vertical 
center lines of the sheet, Fig. 4. 

Dimensions. The dimension for the border lines on 
all of the work in this course will be ll"xl7". Size of 
sheet when finished, 12"xl8". See Fig. 4. 

T-SQTJARE 

(4) Construction. Both the blade and the head of 

the T-square, Fig. 5, are of hard wood, hence the glue 


8 


MECHANICAL, DRAFTING 



















USE OF INSTRUMENTS. 


9 


cannot cement them very tightly together; neither do the 
short screws hold very firmly; a fall, even to the floor, 
may break the joint and damage the T-sqnare. Keep the 
T-square out of danger of any snch fall. 

In case the joint breaks, take ont screws, rough both 
head and blade with coarse sandpaper, coat well with 
Lepage’s glue, place blade at 90° with head with triangle, 
tighten screws and let stand a day. Then take out screws 
and put in round-headed wood screws long enough to run 
through and project an eighth of an inch or more. File 
off screws carefully. Be sure screws are tight. It may 
be advisable to bore small holes entirely through head 
and blade for these large screws, to prevent splitting of 
the wood. 

Position on board. In drafting, a right-handed man 
should keep the head of the T-square to the left, Fig. 6, 
in order that he may handle it with his left hand, leaving 
the right free for drafting. Never place the T-square in 
any other position on the board, as the edges of the board 
seldom form a rectangle nor is the head of the T-square 
likely to make exactly 90 degrees with the blade. 

Use of blade. The upper edge of the blade should be 
used for drafting only; and the draftsman will do well 
to take excellent care of this edge, for once niched or 
dented the instrument is practically ruined for good work. 
The lower edge may be used as a cutting ruler but never 
for drafting. 

Position when not in use. Any draftsman profits by 
keeping his drawing instruments in certain definite 
places, so that as far as possible he may keep his atten¬ 
tion entirely on his work, handling his instruments sub¬ 
consciously. It is found most convenient to slip the 


10 


MECHANICAL DRAFTING. 




use: of instruments. 


11 


T-square to the bottom of the board, when not in use; it 
is here out of danger, out of the way, yet easily accessible. 

To keep clean. A drawing may easily be smudged by 
a dirty T-square, so it will be well to give the blade a 
thoro cleaning with a damp cloth or piece of art gum at 
frequent intervals. 


SCALE 

(5) Care. The scale should never be used as a 
ruler because, as a drafting instrument its efficiency 
depends upon the condition of its edges, and these edges 
can easily be defaced by misuse and the instrument badly 
damaged. Furthermore, the boxwood of which the scale 
is made warps quite easily; hence, the edges of a tri¬ 
angular scale will seldom be found perfectly straight. 

Use. On inspection, Fig. 7, it is seen that the numer¬ 
als are all placed on the scale so as to appear upright 
only when one works over the top of the scale or on the 
edge away from the draftsman and not toward him. All 
dimensions should be taken directly from the scale as it 
lies on the drawing and not by means of the dividers. 
The needle point is the best aid in obtaining dimensions 
with perfect accuracy. The pencil point is a poor sub¬ 
stitute for the needle point. 

NEEDLE POINT 

(6) From Richter Set. An excellent needle point 
for obtaining dimensions may be made up by inserting 
into the long knurled barrel furnished with every set of 
Richter instruments, the small point which is provided 
for converting the large compass into a set of dividers, 
Fig. 8. 


12 


MECHANICAL, DRAFTING. 



















































USE OF instruments. 


13 


To make in shop. A feedle 'point may be easily made 
from a strip of white pine % // x 1 / 4' / x2" and a medium size 
sewing needle. 

Construction: Fig. 9. Insert the needle in a vise, 
point down, with about %" of the point in the vise, and 
carefully drive the strip of pine over the exposed part 
of the needle; the wood may then be shaved round and 
pointed slightly at the needle end. 

TRIANGLES 

(7) In drawing vertical lines with triangles the ver¬ 
tical edge should always be to the left or toward the 
head of the T-square, Fig. 10. 

PENCILS 

(8) Numbering. Before, sharpening either end of 
the pencil, cut with a pen knife a number of nicks toward 
the center to correspond to the degree of hardness; e. g., 
four nicks for 4H, six for 6H, etc., Fig. 11. 

Sharpening wood. In sharpening, trim the wood 
carefully on both ends of the pencil, back a distance of 
about one inch from the ends, leaving about of the 
lead exposed, Fig. 12. One end is to be sharpened to a 
round point, the other to a wedge. In shaping up both 
of these points, use the pencil point tile provided in 
the kit. 

Round point. In shaping up the round point, hold 
the pencil at an angle of about 45 degrees with the axis 
of the tile. As the lead travels over the tile, Fig. 13, 
revolve the pencil slowly between the thumb and fingers, 
attempting to give it a complete revolution with each 
stroke. The lead may thus be easily sharpened to a per¬ 
fect cone. In this sharpening be careful that the point 
extends the full length of the lead exposed. 


14 


MECHANICAL DRAFTING. 



Pound PoinT 


wedge PoinT 



Stems 


Left Right Under 

Diagonal© Horizontql 1 Hooh | HooKS Over Hook 


c ) r j 


* . ^ 
Right line 


5 6 

C urves 


Fig. 15 


CapiTal 


O 


-^2 

lower case letter 





























USE OF instruments. 


15 


Wedge point. In sharpening the wedge point hold 
the pencil perpendicular to the axis of the file, Fig. 14, 
and so inclined to the plane of the file that the lead may 
be sharpened the full quarter inch exposed. 

Use of points. The round point should he used for 
drawing short lines and lettering, the wedge point for 
long lines; the round point dulls rapidly in drawing a 
long line and will make a line of varying weight. 

ERASERS 

(9) If an eraser becomes apparently greasy and 
smudges instead of cleans a drawing, it may easily be 
cleaned by rubbing it with another eraser or by rubbing 
it on the rough surface of the drawing-board itself. 

OFFHAND LETTERING 

(10) Offhand letters, tho apparently complex in 
their construction, when analyzed into their component 
parts, are found to be composed of just seven elements, 
Fig. 15; three of these are right lines, and four, com¬ 
paratively simple curves. 

Height of letters. From the printer’s custom of keep¬ 
ing the capital and small letters in different parts of his 
type case they have quite generally become known as 
capitals, and lower case letters, Fig. 16, rather than small 
letters. Letters may be of any height; however, .in every 
case the height of the lower case letters, Fig. 16, is two- 
thirds of the height of the upper case or capital letters. 
Dimensions for letters are hence given as 3/T6"xl/8", 
l/8"xl/12", etc., the first dimension giving h, the height 
of the capital, the second 2 /3h, the height of the lower 
case letters. 


16 


MECHANICAL, DRAFTING. 



















































































use: of instruments. 


17 


Width of letters. If the height of the letter, for 
example the capital, be divided into five equal parts, one 
of these five equal parts is known as a unit space, Fig. 18. 
If then a rectangle be constructed with a height equal to 
the height of the letters and a width of four unit spaces, it 
will enclose each of the letters of the alphabet except 
E, F, P, R, M and W; that is, all of the letters of the 
alphabet except E, F, P, R, M and W are four unit spaces 
wide, E, F, P and R three and one-half units, and M and 
W five. The same is true of the lower case alphabet; it 
must be understood, however, that in the lower case 
alphabet, the width of the letter will be four-fifths of the 
height of the lower part of the letter, Fig. 19. The length 
of the long stems will have no effect on the width of the 
letters. 

Distorted letters. Letters whose width, as has just 
been explained, is four-fifths of the height are known as 
normal letters; if the width of the letter be less than this 
four unit spaces, it becomes a distorted letter and is 
known as a compressed letter; if on the other hand the 
width is greater than four unit spaces it becomes an 
expanded letter. 

COMPONENTS OF LETTERS 

(11) Stems. The vertical components of letters are 
known as stems; if they have a length equal to the height 
of the capitals they are known as long stems, Fig. 20, 
and enter into the composition of such letters: B, D, T, 
b, h, p, q, etc. If the stem has a length equal to the 
height of the lower case letters it is known as a short 
stem; such stems of course enter into the composition of 
only the lower case letters. In making either of these 
stems with either the pen or pencil, the direction of the 
stroke is down. 


18 


MECHANICAL DRAFTING. 


Left diagonals. If in a rectangle with a height equal 
to the height of either the capital or lower case letters 
and width equal to four-fifths of this height, Fig. 21, a 
diagonal be drawn from the upper right to the lower left 
corner, we have what is known as a left diagonal, from 
the direction of the stroke in formation. Such diagonals 
enter into the composition of the letters x, z, v, y, M, 
W, V, etc. 

Right diagonals. The diagonal from the upper left 
to the lower right corners of the rectangle just men¬ 
tioned, Fig. 21, is known as a right diagonal, from the 
general direction of the stroke in formation; this diag¬ 
onal enters into the composition of letters x, y, h, etc., 
also N, M, W, etc. 

Horizontals. The horizontal components of such let¬ 
ters as H, L, E, F, etc., are known as horizontals; the 
direction of the stroke in formation is from left to right. 

Left hooks. If the letter 0 be cut in half by a ver¬ 
tical line, Fig. 22, the left half is known as a left hook, 
the direction of the stroke being from the top toward the 
left, down, then toward the right; this component, with 
slight variations, enters into the formation of the lower 
case letters a, c, d, e, g, o, q and 5 . 

Right hooks. The right half of the letter 0, Fig. 22, 
is known as a right hook, the direction of the stroke 
being from the top toward the right, down, then to the 
left. This component enters into the formation of the 
capital letters D, P, 0, Q, R and S, and lower case letters 
b, p, o and s. Tho apparently no more difficult to form 
than the left hook, this right hook seems to present the 
main difficulties of the alphabet; for the letters b, p and 
s are the most difficult in the whole alphabet to form 


USE OF instruments. 


19 


properly and in this group the letter b seems to be the 
most difficult; tho apparently identical in construction 
with the letter p, b is in fact the bugbear of every man 
learning to letter and should receive the most practice. 

Under hooks. If the capital letter U he cut in half 
by a vertical line, Fig. 23, the left half is known as a 
right under hook, the direction of the stroke being down 
and to the right. The right half of the letter U is known 
as a left under hook, the direction of the stroke being 
down and to the left. These two components do not pre¬ 
sent any great difficulty to the average draftsman and 
the letters u, g, j and y, J and U, of which they are the 
chief components, will not need a great amount of 
practice. 

Over hook. The curved component of the lower case 
letter h is known as an over hook, Fig. 24, the direction 
of the stroke being to the right and down; this compo¬ 
nent enters into the formation of the letters h , m, n and r. 

(12) The most difficult letters. The most difficult 
letters to form perfectly are found in the lower case 
alphabet and are, in the order of their difficulty, b, p, y, 
s, r and g. As has been mentioned before the letter b 
seems far more difficult to form than the letter p and 
should receive the bulk of the extra practice. 

Easy style of letter. To the beginner, the normal 
style of letter, with a width of four-fifths of the height, 
seems to be extremely difficult to form, while the expanded 
style, Fig. 25, has a number of distinct advantages; per¬ 
haps the fact that horizontal lines prevail in actual life 
makes these expanded letters easier of formation, the 
horizontal predominating in this style. Furthermore, 
expanded letters have a most excellent appearance irre- 


20 


MECHANICAL DRAFTING 






Boll Roirvt Ben 


Old Reliable Pen 



Ball 



Fig. 28 

















































































USE OE INSTRUMENTS. 


21 


spective of the extent to which they have been expanded; 
that is, no matter how great the distortion may be, the 
effect is invariably good; for these reasons the beginner 
will find it well to adopt this expanded style; at least 
until the formation of the letters has become a habit. 

NUMERALS 

(13) Height. When numerals are used with letters 
they are given a height equal to the height of the capi¬ 
tals, Fig. 26. 

Fractions. Theoretically the height of the numerals 
of a fraction should not be as great as the height of 
integral numerals; however, dimensions do not look at 
all out of proportion when all of the numerals, whether 
fractional or integral, are given the same height. Guide 
lines should be ruled for the integral numerals, Fig. 27 ; 
however, they need not be ruled for the fractions, as the 
heights of these can easily be approximated. 

LETTERING PENS 

(14) Styles. The styles of pens that have been 
found best for lettering are shown in Fig. 28. The ball 
point makes a rather heavy line; however, it has the dis¬ 
tinct advantage of making a line of very uniform weight 
and works well for beginners. With the old reliable 
pen it is possible to make lines of much lighter weight 
and this pen is usually preferred by draftsmen. To those 
who have a great amount of lettering to do the writers 
recommend Moore’s Non-leakable fountain pen; from 
severe trials it has been found to work with perfect sat¬ 
isfaction and its convenience cannot be over estimated. 
A medium fine pen makes the most uniform letters. 


22 


MECHANICAL, DRAFTING 








































USE OF INSTRUMENTS. 


23 


CLEANING PADS 

(15) Chamois roll or block. Inasmuch as water¬ 
proof drawing ink dries so rapidly the pen should be 
cleaned thoroly with cloth or chamois before each refill¬ 
ing. In addition to this cleaning it will be found possi¬ 
ble to obtain more clear cut letters if after each three or 
four letters the point of the pen is scraped over a piece 
of chamois. A convenient scraper may be made by roll¬ 
ing up a 2"x4" piece of chamois and binding it with a 
rubber band, Fig. 29, or by pasting a 2"x2 // piece on a 
small block of wood. 



Fig. 29 



24 


MECHANICAL DRAFTING. 


LESSON 2 

USE OF INSTRUMENTS 

LARGE DIVIDERS 

(16) Adjustment of the points. With Richter 
instruments it will always be found possible to adjust the 
points of the various tools to any desired length; so, 
before attempting to use the large dividers be sure that 
the points are adjusted to exactly the same length and 
that they are in perfect shape. In case the points of the 
Gem Union instruments are not of the same length, it 
will be necessary to grind the long point down on a small 
carborundum stone. Keep points always in perfect shape 
for good work. 

Opening and setting. It is desirable always to handle 
each instrument with the right hand unaided by the left; 
this permits of much more rapid work and the habit is 
not difficult to acquire. To open the divider, insert the 
thumb between the legs, prying them apart a short dis¬ 
tance until the fingers may be inserted and the one leg 
grasped between the first and second fingers, the other 
between the third finger and the thumb; the head of the 
instrument should rest against the knuckle of the first 
finger. Holding the instrument in this position it is 
found easily possible to adjust the points to any desired 
distance. 

To place point. To place the one point of the divider 
at any point on the sheet, rest the wrist at a convenient 
distance from the point; it will then be found easily pos¬ 
sible to place the point of the leg between the third finger 
and the thumb in any desired position. Raising the 


use OF instruments. 


25 


wrist and keeping the little finger on the paper, the other 
leg can now be adjusted for any desired distance. It is 
perhaps as good practice and may be found easier for 
some to steady the hand thruout the operation by merely 
resting the little finger on the paper, instead of the wrist. 

Stepping off distances. After the points have been 
placed as desired, to step off a certain distance a num¬ 
ber of times, raise the first finger to the top of the head, 
then, releasing the other leg, grasp the head between the 
first finger and the thumb and step off the distance by 
swinging the dividers alternately over and under. Hand¬ 
ling the instrument in this way it will not be necessary 
to take a new grip on the head thruout the operation. 

BOW DIVIDERS 

(17) Adjustment. (See Adjustment for Large 
Dividers.) 

Placing at center. (See same for Large Dividers.) 

Opening and closing points. With the center adjust¬ 
ment instrument, which is always preferable to the side 
adjustment, after placing the one point at a given point 
on the sheet, raise the first finger to the head and turn 
the adjustment screw between the second finger and 
thumb until the points are apart as desired. 

Stepping off distances. (See same for Large 
Dividers.) 

TRIANGLES 

(18) To clean. The surface of the celluloid tri¬ 
angles quickly becomes smudged from erasings and pen¬ 
cil dirt that may be on the drawing; hence, they must be 


26 


MECHANICAL, DRAFTING. 




Fig. 30 



Fig. 31a 




































US^ of INSTRUMENTS. 


27 


cleaned frequently with soap if the drawings are to be 
kept in good shape. 

Letter guide lines. For the easy ruling of letter guide 
lines without the use of the scale and needle point, it is 
suggested that along the edges of the 30x60 triangle 
light lines be scratched with the needle point as follows: 
Along the hypothenuse and 1/8" from the edge scratch 
carefully a fine line; also a second line 3/16" from the 
edge scratch a single line, and a second line 1/8" from the 
edge, Fig. 30. After the lines have been scratched they 
should be smeared over with India ink, rubbing the ink 
into the scratches with the fingers. After the ink has 
dried for a few minutes the surplus may be rubbed off 
with a cloth. Turning the triangles over with the 
scratched lines against the paper, it is seen that they 
now stand out very sharply and may be used in ruling 
guide lines for any necessary lettering. 

Parallel and perpendicular lines. In Fig. 31 are 
shown a number of methods of obtaining a series of 
parallel lines, or lines perpendicular to given lines, by 
means of the triangles and T-square. 

BOW PENCIL 

(19) Hard lead. To obtain satisfactory work from 
the boiv pencil the lead should be extremely hard, at least 
6H. Ordinarily, the lead supplied with instruments is 
not more than 2 or 3H and wears down too rapidly. Try 
the lead before using it on a drawing and if found soft 
substitute for it a piece of lead from a 6H pencil. 

Sharpening lead. Adjust the lead until it is the same 
length as the needle point, then shape up the wedge point 


28 


MECHANICAL, DRAFTING. 



Fig. 32 To sharpen Lead 




Effect of position 2. 


InH ran under T square 
Fig. 36 


E/Ff ecT of position 3 


Pen riding on one Nib 
Fig. 37 
































US^ of instruments. 


29 


as shown in Fig. 32. Grind the outside bevel at an angle 
of about 30 degrees until the cut has run about three- 
fourths across the end of the lead; then tip it off slightly 
at a similar angle on the inside. The lead, thus sharp¬ 
ened, both wears well and gives most satisfactory work. 
Never sharpen the lead of the compass or bow pencil to 
a round point. 

Adjustment to any radius. In adjusting the points 
to any desired radius, instead of obtaining the dimension 
directly from the scale, it will he better to transfer this 
radius to the paper by means of the scale and needle 
point, and set the bow pencil from this as explained 
under Large Dividers. 

Describing arcs. In describing an arc with the bow 
pencil, the direction of motion of the lead should he clock¬ 
wise and thru the total length of the desired arc before 
taking the lead from the paper. See Fig. 33. 

RULING PEN 

(20) Manner of holding. The ruling pen should be 
held between the first and second fingers and thumb as 
shown in Fig. 34. In ruling lines, the adjusting screw 
should he turned from the user. 

Position of pen. Unless Care is taken to keep the pen 
in a vertical plane thru the edge of the T-square blade or 
edge of the triangle, Fig. 35, trouble may he experienced 
in the ink running under the T-square blade, Fig. 36, or 
in a badly broken line, Fig. 37. 

Tilted in the direction of motion. For best results 
the pen should be tilted slightly in the direction of the 
motion, Fig. 34; this permits one to inspect the work of 


80 


MECHANICAL DRAFTING. 








































USE OE INSTRUMENTS. 


31 


the pen as it travels. A greater angle than 10 or 15 
degrees may however permit the ink to run down and 
cause a blot. 

To fill pen. To fill the pen, always use the quill sup¬ 
plied on the stopper of the ink bottle. Never dip the pen 
into the ink. If by chance any ink has gotten on the out¬ 
side of the pen, wipe it off carefully before using; it may 
save a serious blot. 

Direction of motion in ruling lines. In ruling lines, 
either with the pen or pencil, the direction of motion 
should be from left to right or from bottom to top of the 
sheet, Fig. 38. Ruling lines thus, it is always possible to 
see what the pen or pencil is doing. Never rule lines 
down the sheet unless they are oblique and are being put 
in with the triangle. 


INK BOTTLES 

(21) Holder. A convenient holder for the ink bot¬ 
tle may be made from two sheets of blotting paper and 
a rubber band as shown in Fig. 39. A holder of some 
kind is advisable and one such as this answers a double 
purpose. A holder of the style shown in Fig. 40 may be 
purchased from any of the instrument companies. 

Closed when not in use. India ink is very heavy and 
dries quite rapidly; hence, if the stopper is left out of 
the bottle even for several hours the ink may become so 
heavy as to make it impossible to obtain good work from 
it. Be sure to close the bottle carefully after each refill¬ 
ing of the pen. 

To open bottle and fill pen. To open the bottle with¬ 
out danger of upsetting, grasp the neck between the third 


32 


MECHANICAL DRAFTING. 







c 



X 


> 

A 



a 

A 


£ 


>1 

X 

c 



5 


y 

y 



x 

x 


s 

. 

s 

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\ 



S 










7 

1 , 

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5 


a 

X 



A 

Ay 


X 



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a 

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X 



(A 




X 




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2 


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F s ;=- 


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=1 


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2 X 

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^77 

2 T 5 

XX 

§..§ 

^ i 7 




2 2 5 

s s 

§ £L 

x 2 


x 5 

X 

X 

2 


X "- 

x. 7 

\. 

7 T 5 

XT X 

y x 

2\ 7N 

e 2 

7~*\ 


.. <• 

v 


'x 

f- A 

X A 


1 - 

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t'-n 2 S 

% 22 


X 

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use; of instruments. 


83 


and little fingers, Fig. 41, and the stopper between the 
first finger and thumb of the same hand; after removing 
the stopper, place the quill between the nibs of the pen 
and fill as desired. 

MECHANICAL LETTERS 

(22) Little need be said in explanation of the fol¬ 
lowing alphabet of mechanical letters, Figs. 42 and 43; 
this style is given mainly for its simplicity of construc¬ 
tion, and tho perhaps slightly defective in minor details, 
the letters, when combined into words according to the 
scale in Lesson 3, will have a very symmetrical and 
uniform appearance. 

UNIT SPACE 

If the total height of the letter be divided into five 
equal parts, one of these five parts is known as a unit 
space. In construction, these unit divisions may be 
obtained as shown in Fig. 44. For rapid and easy con¬ 
struction of block letters, all of the space lines thru 4 1? 3 1? 
2j and 1 1 should be ruled in; however, these lines should 
be very light. 

WIDTH OE LETTERS 

Inspection of the alphabets, Figs. 42 and 43, shows 
that each letter of the alphabet except E, F, P, R, M and 
W is four unit spaces wide, while E, F , P and R are three 
and one-half and M and W five. The alphabet is hence 
so simple that its details can easily be memorized. 

THICKNESS OF LETTERS 

In every case, whether the letter be normal, com¬ 
pressed, or expanded, the thickness may be kept one unit. 


34 


MECHANICAL, DRAFTING. 


If space permits and it is desired, any new nnit may be 
chosen for obtaining an exaggerated width of the letter, 
Fig. 45; however, all radii of arcs and the thickness of 
the letter are in terms of the unit space. The same is 
true of a compressed letter. 


^Fixed Unit 



7 ^ 






ij 












y 


~i iji ir f 

Arbitrary Unit 


Fig. 45 


















NAME PLATES AND TITLES. 


35 


LESSON 3 

NAME PLATES AND TITLES 

(23) Name plates. A name plate for any machine 
or piece of structural work should contain the following 
information: Name of the machine (unless it is so com¬ 
mon as to be perfectly familiar to everyone), name of 
the manufacturing company, and address or location of 
the company’s works or factories. 

(24) Drawing titles. A working drawing title 
should contain the following information: Name of the 
piece of machinery drawn, name and address of the 
manufacturing company, initials of the draftsman, 
checker, and tracer, scale, drawing number, and other 
necessary filing data. 

GENERAL ORDER OF WORK IN CONSTRUCTION OF 
WORKING DRAWING TITLE 

(25) Given data. In making up a working draiving 

title the draftsman ordinarily has given him a certain 
amount of data as.follows: “Details of Horizontal Mill¬ 
ing Machine, manufactured by the Landis Tool Company, 
Waynesboro, Penna; drawn by (R. C. S.), checked by 
(-), traced by (-), scale y 2 "=l", draw¬ 

ing finished April 2nd, 1915. ’ ’ The above material, con¬ 
densed, must be placed within a given title space, per¬ 
haps 3"x5". 

Elimination of unnecessary material and arrange¬ 
ment into groups. In order that the given material may 
he placed within the given title space, every unnecessary 




36 


mechanical, drafting 



- 


mm 


. r :; :; Af.' . ; 
? Is# &• 

■ 






. . ■ 


#8 3 *. *£«Y »*?¥. MiU<M KMitlttC 

m%9 mn. 

W t W 3 n. 

ns** & mi*n *n tfa, nmm*tt> «, u » s. a, 















NAME} PI,ATe:S AND TITLES. 


37 


word must be eliminated. Running thru the given data 
it is seen that the words italicized can be omitted 
without the least danger of misunderstanding the 
remainder. With these words omitted the remaining 
data seems to group itself naturally as follows: 

(1st prom.) Horizontal Milling Machine. 

Details 

(2nd prom.) Landis Tool Co. 

(3rd prom.) Waynesboro, Pa. 

Drawn by (-), Checked by (-), Traced by (-), 

(4th prom.) Date (-), Scale (-). 

Order of prominence. In a drawing title as well as 
in a name plate, certain groups of words are more impor¬ 
tant than others. In the drawing title the name of the 
piece of machinery is, of course, given most prominence; 
while, in the case of the name plate the name of the manu¬ 
facturing company should be given first prominence. In 
the drawing title the name of the manufacturing com¬ 
pany will be given second prominence, address of the 
company third, and the remaining information, being 
about equally important, should be given least prom¬ 
inence and arranged as desired. The word “Detail” or 
“Assembly”, which may be either included or omitted 
as desired, will not figure in the order of prominence. 

Methods of securing prominence. In both advertis¬ 
ing and drafting there are in use two methods for secur¬ 
ing prominence of any one group of words over another. 
The one most generally used is variation in height of 
the letters of the various groups, to correspond in general 







38 


MECHANICAL DRAFTING. 













































































NAME PLATES AND TITLES. 


39 


to the order of prominence established; if this is not 
possible thru lack of space, a distorted letter, either of 
odd construction or of the compressed or expanded style, 
may be used. One may then depend on the odd appear¬ 
ance of the letters to give to that group of words the 
desired prominence. In the case of drawing titles and 
name plates the first method, i.e. variation in height of 
letters is preferable. 

Margins and margin lines. Before sketching in the 
guide lines for the various groups of words, margin 
spaces should he determined and light margin lines ruled 
in Fig. 46. In doing this certain rules of design must be 
adhered to; the upper and lower margins may be of any 
desired width; however, for best appearance they must 
be equal. The right and left margins, tho not necessarily 
equal to the upper and lower, must be equal to each other. 
In a rectangular space whose width is greater than the 
height, better effect is obtained if the right and left mar¬ 
gins are made slightly greater than the upper and lower; 
if the reverse is true of the rectangle then the right and 
left margins should he less than the upper and lower. 

Guide lines. To obtain the guide lines for the various 
groups of words, produce the lower margin line to the 
left until it intersects the border of the title space at A, 
Fig. 46, and from this point draw up and toward the 
right a line at an angle of about 60 degrees with the 
horizontal. Selecting any desired distance as the rela¬ 
tive height of the letters of the lower group, lay off this 
distance from A along the 60 degree line; then a relative 
distance for the space between this line and the line next 
above; next a relative space for the letters of the next 
group and so on until all of the groups have been 
accounted for along the 60 degree line. From the last 


40 


MECHANICAL, DRAFTING. 


i - 

I 
I 
I 

X 

~V^ 


S A 4 4 3l£ 4 4 4 3'/fe A 

WAYNESBORO 

O o 1/2 I I I I I I 5 

To-t-ol =50 '/2 Half = 20 3 / 4 

Fig. 47 


w 

1 A 

' Y "N ' 1 E 1 1 5 1 1 q 1 1 o 1 

Scratch Paper 

1 R ' 

1 o 1 

1 P » A ' 



Fig. 48 




—J- 

1 

Guide l_ines 

J_1 

1 1 

1 II 1 ' 

1 

w 

' A 

’v" n m e."s"b"o' 

Scratch Paper 

1 R ' 

1 o 1 

1 P " A ! 


3'/a 4 

P A. 

i/a 
























NAME) PLATES AND TITLES. 


41 


point, B, draw a line, B C, as shown in figure and from 
the various points along the line A B draw lines parallel 
to B C until they intersect the border line, A C; the re¬ 
quired guide lines will then be found the same relative 
distances apart as the points plotted on the line A B. 

Spacing of letters. Before attempting to place in any 
of the letters the value of the unit spaces of the various 
groups of letters must he determined. Tho the various 
lines of letters may not require all of the horizontal space 
allotted to them, for best appearance they must he placed 
centrally; i.e., with equal margins at their right and left. 
To accomplish this, rule in a vertical center line of the 
title space and use either of the following methods: 

(1) MATHEMATICAL METHOD 

Taking for illustration the group “Waynesboro, 
Pa.”, sketch roughly the letters of these two words on a 
piece of scratch paper, spacing liberally, Fig. 47; next 
place above each letter its width in unit spaces and be¬ 
tween the various letters the number of spaces required 
to separate letters, obtaining these from the table, Fig. 
49. Between the two words allow at least five unit spaces. 
The sum of all of these spaces is 59%; one-half of 59% 
is 29%; stepping off 29% spaces to the left from the cen¬ 
ter gives us the point at which the letter W of this line 
should start. 

(2) SCRATCH PAPER METHOD 

Select any point close to the left end of the straight 
edge of a sheet of scratch paper, Fig. 48, and from this 
point step off with the large and small dividers the 
proper number of unit spaces in succession, for the vari¬ 
ous letters and spaces between letters, marking with the 
divider points the location of the beginning and end of 


42 


MECHANICAL, DRAFTING. 


each letter. Placing the scratch paper centrally along 
the lower gnide line of the space into which this group of 
letters is to go, mark with the needle point the position of 
the beginning and end of each of the letters. This 
method has the advantage of centrally placing the entire 
group and of locating the various letters at the same 
time. 

TABLE OF LETTER SPACES 

(26) To obtain the space, in units, to be allowed 
betiveen any letter, e.g. A, and any letter of the alphabet 
which may follow it in a word, it is seen in the table, Fig. 
49, that between A and any letter of the alphabet except 
T, V, W and Y, should be left one-half unit space, while 
between A and T, V, W or Y, no spacing should be left. 
In every case the spacing given is that to be allowed be¬ 
tween the letter given in the first column and any letter 
of the alphabet which may follow it in a word. 


Fig. 49 

Table of Block Letter Spacing 


u 

<v 

<u 

a 

Regular 

Spacing 

Spacing 

for 

Exceptions 

Exceptions 

I 

1 

Regular 

Spacing 

Spacing 

for 

Exceptions 

Exceptions 

A 

1/2 

1 o 

T, V, W, Y 

N 

1 

| 1/2 

A, T, V, W, Y 

B 

1 1 1 

1/2 

A, T, V, W, Y 

o | 

1 

1/2 

“ 

C 

I 1 1 

1/2 

“ | P 

1 

1/2 

“ 

D 

1 

| 1/2 

■IQ 

1 

1/2 

“ 

E 

1 

1/2 

“ | R 

1 

1/2 

“ 

E 

| 1/2 

0 

A 

s 

1 

1/2 

“ 

G 

| 1 

1/2 | A, T, V, W, Y 

T 

1/2 

0 

A, J 

H 

1 1 

1/2 

“ 1. u 

1 

1/2 

A, T, V, W, Y 

I 

1 1 

1/2 

“ I V 

1/2 

o 1 

1 A, .T 

J 

1 . 1 

| 1/2 

“ 1 w 

1/2 

0 1 

K 

i 1 

| 1/2 

A, 0,T,V, W,Y 

X 

1 

1/2 | A, 0,T,V, W, Y 

E 

| 1/2 

1 o 

T, V, W, Y 

Y 

1/2 

0 

1 A, J 

M 

1 1 

| 1/2 |A, T, V, W, Y 

Z 

1 1 

1/2 | A, T. V, W, Y 
































ORTHOGRAPHIC PROJECTION. 


43 


LESSON 4 

ORTHOGRAPHIC PROJECTION 

(27) Definition. Orthographic Projection, the 
branch of geometry employed in the making of work¬ 
ing drawings y may be termed the “science of propor¬ 
tional drawings.” This definition means little without 
some further explanation; however, it is perhaps well to 
give it at this time as a foundation on which to base 
further discussion. 

PRINCIPLES OF ORTHOGRAPHIC PROJECTION 

(28) It is seen from Fig. 50, which is a representa¬ 
tion of a cube constructed by the principles of Descrip¬ 
tive Geometry, applied in what is known as Perspective, 
that, tho the object is represented as we are accustomed 
to see it, the picture gives us absolutely no conception 
of the ratio of the several parts of the object to each 
other; i.e., tho the sides of the small square recess in the 
top may appear to be half the length of the edge of the 
cube, one has no means of knowing exactly what the rela¬ 
tion is; hence, unless actual dimensions were given for 
every detail of such a drawing and these dimensions 
could be depended upon as being absolutely accurate, one 
would have no means of making, except approximately, 
the object which the drawing represents. Hence, it will 
be appreciated that in making drawings for the use of 
workmen in shops, such an application of Descriptive 
Geometry should be employed as will represent each line 
of the object at.least once, in its true mathematical ratio 
to other lines; i.e., such a representation, that if no 


44 


MECHANICAL, DRAFTING. 



Fig. 50 



Fig. 51 


















ORTHOGRAPHIC PROJECTION. 


45 


dimensions were given, one could compare lines by means 
of a scale or dividers and be certain of their exact ratio 
to each other. This branch of Descriptive Geometry is. 

known as Orthographic or Proportional Measurement 
Projection. 

Orthographic projection. To obtain such a projec¬ 
tion of the cube represented in Fig. 50, let us imagine 
that we have suspended the cube in space with the face 
containing the square recess horizontal; then, see Fig. 51, 
let us imagine that four planes be drawn about this cube 
in the positions shown, one, a horizontal plane, a second a 
vertical plane parallel to the face of the cube containing 
the circular recess and two other planes perpendicular to 
both the vertical and horizontal planes just drawn. 

Coordinate planes and coordinate angles. The four 
planes just constructed about the cube, Fig. 51, are 
known in orthographic projection as coordinate planes 
and are named individually, the Horizontal or H plane, 
Vertical or V plane, Profile or End plane. The four 
diedral angles formed by the H and V planes are known 
as 1st, 2nd, 3rd, and 4th and are numbered in the order 
shown. 

Projections or orthographic representations. Before 
proceeding with the explanation of the manner of obtain¬ 
ing the proportional drawings, a fact of geometry should 
perhaps be called to mind; i.e., the point is the origin of 
all geometric conceptions, including lines, planes, and 
solids; for, if a point moves thru space in a fixed direc¬ 
tion it generates a right line; if this line be moved thru 
space in a fixed direction it generates a plane, and if this 
plane be moved thru space it generates what we com¬ 
monly call a solid; hence, in making representations of 


46 


MECHANICAL DRAFTING. 


I 2 

























ORTHOGRAPHIC PROJECTION. 


47 


any object we find it possible always to simplify the work 
by making the representations of the various significant 
points of the object and connecting these points by right 
lines, etc., Fig. 52. 

In explaining the method used in obtaining the 
orthographic representations of a cube, the corner A, 
Fig. 53, will be taken as typical of all significant points of 
the object. It is desired to represent this point on each 
of the three coordinate planes, the second End plane be¬ 
ing for the time eliminated. From point A are dropped 
three perpendiculars, one to each of the coordinate 
planes; the points in which these perpendiculars pierce 
these coordinate planes are known as the projections of 
point A, and are called, V or Vertical projection or 
Front View ( always lettered a' if lettered at all), H or 
Horizontal projection or Top View ( always lettered a 
if lettered at all), and Profile, End Projection, End or 
Side View ( always lettered a" if lettered at all); if then 
from all of the points of the object perpendiculars were 
dropped to the Vertical plane and lines drawn connecting 
the piercing points of these perpendiculars in regular 
order, Fig. 53, we would have on the Vertical plane a 
draining or projection representing perfectly the appear¬ 
ance of the front of the cube; a similar process would 
give us on the Horizontal plane a correct representation 
of the Top of the object and on the End plane a repre¬ 
sentation of the side of the object. 

1st, 2nd, 3rd, and 4th angle projections. If the point 

be placed in the first angle, as in Fig. 53, the projections 
a, a', and a" are known as First Angle projections. 
Projections b, b', and b" of point B in the second angle, 
Fig. 54, are known as Second Angle projections; c, c', 
and c", the projections of point C in the third angle, Fig. 


48 


MECHANICAL DRAFTING. 























ORTHOGRAPHIC PROJECTION. 


49 


55, are Third Angle projections; and d, d', and d" of 
point D in the fourth angle, Fig 56, are known as Fourth 
Angle projections; i.e., the projections of a point are 
known as First, Second, Third, or Fourth Angle projec¬ 
tions according to the angle in which the point is placed. 

Revolution of coordinate planes. Already an appar¬ 
ent difficulty has arisen in the question of how to repre¬ 
sent all of these projections, e.g. of point A, Fig. 53, on a 
single sheet of paper when in fact the three projections, 
a, a' and a", are found on three planes at right angles to 
each other. The line of intersection of the Horizontal 
and Vertical planes is known as the Ground Line or G L; 
the intersection of the Vertical and End planes is G a h v 
This difficulty can now be solved as follows: Using G L 
as an axis, Fig. 57, let us imagine that the portion of the 
H plane in front of V is revolved down, the portion be¬ 
hind, up until it coincides with the V plane. In this revo¬ 
lution, a, Fig. 57, revolves into the new position, a, on 
the continuation of the perpendicular dropped, from a' 
to G L; for, if thru the two lines A a and A a', a plane 
be passed, Fig. 58, it will cut from the V plane a line 
thru a' perpendicular to G L; as a revolves about G L 
down, it revolves in the plane a' A a, and when it reaches 
the V plane, must lie on the perpendicular to G L thru 
a ', the line cut from the V plane by the plane a' A a. Since 
a is before G L the distance Aa', a will be found below 
G L the same distance; a' is above G L the distance A a; 
hence, the distance from G L to the points a and a' repre¬ 
sents the exact distances which the point, of which these 
are the projections , is from the V and H planes. If then, 
G, Lt be used as an axis and the portion of the Profile 
plane in front of V be revolved to the right, a" comes 
into the new position a", a distance to the right of Gj V 1 


50 


MECHANICAL, DRAFTING. 



1st Angle Projection 


Fig. 59 


c I- 

1 

1 

1 

<3, 

A 

\ 

1 

<3 1 

1 

~T~ C 

i 

1 

1 

c'~ 

i 

lc" 

1 . 

3rd Angle Projection 


Fig. 61 




G, 

g ; 

l 

^1 L 
/| 

1 

d<- 

! 

O' 1 - 

id" 

i • 


4th Angle 'Projection 
Fig. 62 




Fig. 63a 















































ORTHOGRAPHIC PROJECTION. 


51 


equal to A a' and a distance above G L equal to A a, or on 
the horizontal line thru a'. Transferring these revolved 
positions to a new figure, Fig. 59, we have the point A in 
the first angle represented by the three projections, a ' 
above G L, a below GL, and a" to the right of Gj lu 1 and 
above G L. In a similar revolution the projections of 
point B, Fig. 54, would revolve into the positions b, V, b", 
Fig. 60; however, in this case both b and b' are above 
G L. The projections of point C, Fig. 55, revolve into 
the positions c, c', and c", Fig. 61; in this case c' is below 
G L and c above, the reverse of point A in the first angle. 
The projections of point D, Fig. 56, all fall below G L, 
Fig. 62, the reverse of point B in the second angle. 

Projections of objects. Advancing from the points 
A, B, C, and D just discussed, to the objects of which 
these points are elements, we find the projections of the 
cube, when placed in the first angle, to be as in Fig. 63. 
When placed in the second angle, to appear as in Fig. 64, 
third angle, Fig. 65, and fourth angle, Fig. 66. When the 
coordinate planes are revolved in each of these cases the 
projections revolve into the positions shown in Figs. 63a, 
64a, 65a, and 66a. 

Elimination of 2nd and 4th angles. If any of these 
groups of projections or drawings is to be made use of 
in constructing the object, a glance shows that it is 
clearly impossible to make use of the two with the object 
in the 2nd and 4th angles; for, in each case, after the 
revolution the two projections are one over the other, 
producing a hopeless muddle. The choice is then neces¬ 
sarily between the first and third angles. 

Elimination of the first angle. From Fig. 67, it is 

noted that as we ordinarily see objects the top appears 


F~non i~ 


52 


MECHANICAL DRAFTING. 



Front 


































































































ORTHOGRAPHIC PROJECTION. 


53 


above the front and the right end to the right of the 
front or the left end to the left of the front , according to 
the position from which the cube is seen. When the 
object is placed in the first angle and the projections 
revolved into the positions shown in Fig. 63a, it is seen 
that altho the right end projection comes in its natural 
position to the right of the front , the top is under the 
front , an arrangement by no means natural. While, 
when the object is placed in the third angle , Fig. 65, and 
projections revolved as shown in Fig. 65a, the views 
assume a grouping identical with their order on the 
object itself; i.e., the right end to the right of the front , 
and the top above the front. Merely for the sake of this 
natural arrangement the third angle will be selected in 
preference to the first in making working drawings; i.e., 
all working drawings will be third angle orthographic 
projections. 

(29) Summary of principles. It may be well to 
summarize a number of principles brought out in this 
discussion, likewise to mention several violations of pure 
orthographic projection. The top view, Fig. 65a, repre¬ 
sents the exact appearance, with lines in true propor¬ 
tions, of the top of the cube; the front view represents 
the same of the front of the cube, and the side view the 
same of the side of the cube. 

The top and front views must be directly above and 
below each other and the front and end views must be 
on the same horizontal lines as shown in Fig. 65a, if the 
group is to represent the true orthographic projection 
of the cube; a violation of this renders the whole drawing 
incorrect. 

(30) Permissible violations. In Fig. 57, it is 
shown that the portion of the End or Profile plane in 


BBS 


54 


MECHANICAL DRAFTING 














ORTHOGRAPHIC PROJECTION. 55 

front of V is revolved to the right; this of course means 
that the portion of theProfile plane behind V revolves to 
the left; while, in Figs. 65, 65a, the portion of the Profile 
plane behind V is represented as being revolved to the 
right. This revolution to the right of the portion of the 
Profile plane behind V is ortho graphically incorrect; 
however, in the case of the third angle projections it is 
tolerated for the natural order of projections which it 
produces. 

WORKING DRAWINGS 

(31) Definition. A working drawing of a piece of 
machinery is such a group of correctly and completely 
dimensioned orthographic views of that object as will 
give all the information necessary in construction a 
duplicate of the same. 

(32) Detail drawing, defined. A detail drawing is a 

working drawing of one piece of any machine. 

Detail signature. Accompanying each detail draw¬ 
ing, whether the detail drawing be by itself or one of a 
set, should be given a characteristic signature containing 
the following information: Name of the machine part, 
material of which it is made, number of parts required, 
and some arbitrary number for the pattern if the object 
is to he cast. This information should be given in the 
following manner: 

Valve Crank—C. I. 

Reqd.—1. 

Pattern No. A-3. 

The letter A in the pattern number refers to the sheet 
A of the Details of the Corliss engine of'which this valve 
crank is a part; the number A-3, indicates that the valve 
crank is detail number 3 on sheet A. 


56 


MKCHANICAIy DRAFTING. 


























































ORTHOGRAPHIC PROJECTION. 


SECTIONING 

(33) The primary function of orthographic projec¬ 
tion is, of course, to represent the portions of an object 
visible to the eye. Any constructions hidden by the sur¬ 
faces in view may be represented by conventional lines 
known as hidden lines, Fig. 68. The dotted lines in this 
figure represent the three recesses in the top, front, and 
side of the cube. It may be satisfactory to represent in 
this way the interior construction of so simple an affair 
as the object shown; however, if the interior construction 
is in the least elaborate this method is by no means satis¬ 
factory. If an interior construction be represented by a 
number of hidden lines which cross each other, the draw¬ 
ing becomes so vague as to be almost unintelligible. For 
this reason a substitute method has been devised for 
showing any interior or hidden construction. According 
to this method it may at any time be imagined that a 
cutting plane, parallel to one of the coordinate planes, 
can be drawn in any position, cutting away such portions 
of the object as will expose any other parts one may wish 
to see. Ordinarily these planes will be found to pass thru 
some axial line of the object, Fig. 69; however, if desired, 
they may be imagined drawn elsewhere, Fig. 70. This 
process of sectioning is purely imaginary and may be 
represented on only one view of a two or three view 
working drawing, the other views representing the ob¬ 
ject unsectioned by any such plane. The process of sec¬ 
tioning is strictly utilitarian; i.e., one should section only 
objects whose construction can be more clearly explained 
by this process than otherwise. 


58 


MECHANICAL, DRAFTING. 



Fig. 71 


ORDER OF PENCIL WORK 

1— Border Lines 

2— Title Space 

3— Select Scale 

4— View Spaces 

5— Center Lines 

6— Main Outlines 

7— Inside Lines 

8— Aux. & Dimen. Lines 

9— Sec. Lines & Notes 





























ORTHOGRAPHIC PROJECTION. 


59 


ORDER OF PENCIL WORK 

(34) The most rapid progress can be gained in the 
pencil work of a working drawing by following the order 
given in Fig. 71. 

Caution. It is by no means wise to attempt to finish 
one of several views before doing any work on the others. 
Fewer mistakes will be made and more rapid progress 
gained by working on all views at the same time; i.e., 
when a line is placed on one view, its projections in the 
other views should be obtained before proceeding with 
other lines. All views will thus be finished-at practically 
the same time. When one projection of a line is obtained 
from a given dimension, the other views of this same line 
should be obtained by the principle of projection rather 
than by making use of the scale a second time. This 
practise, tho it may permit a mistake to remain unde¬ 
tected, has the advantage of producing drawings which 
are true orthographic projections. 

LARGE COMPASS 

(35) Adjustment. To adjust the needle point of a 
compass to both the pencil and pen, remove the pencil 
point and insert pen; after adjusting the needle point 
so that its shoulder, not the point, is flush with the end 
of the pen, remove pen and inserting pencil, adjust lead 
until it is even with the shoulder of the needle point. 

Sharpening lead. Sharpen the lead of a large com¬ 
pass the same as the lead of the Bow Pencil. Art. 17, 
Lesson 2, Fig. 32. 

Use. For adjustment of leads to any desired radius, 
and placing needle point at any desired center, see Large 


60 


MECHANICAL, DRAFTING. 











ORTHOGRAPHIC PROJECTION. 


61 


Dividers, Art 14, Lesson 2. For describing arcs see Bow 

Pencil, Art. 17, Lesson 2. 

IRREGULAR CURVE 

The irregular curves are those which cannot he drawn 
readily and accurately with the compass. The general 
directions of the different portions of such curves are 
first determined roughly by a number of plotted points 
at as small intervals as possible (the positions of these 
points are obtained either by mathematical coordinates 
or mechanically from other projections or views of the 
same curve). Before drawing the curve mechanically it 
is best to draw lightly a freehand curve thru the plotted 
points, then carefully piece by piece the mechanical 
curve may be drawn. In drawing the mechanical curve 
two things must be kept in mind; first, that the final 
curve must coincide as absolutely as possible with 
the freehand curve; second, that the curve must be 
‘ ‘ smooth, ’ ’ i. e., it must have no sudden glaring changes 
of curvature or “Humps.” The failure of a novice to 
obtain a good irregular curve is due to perhaps two 
causes: first, that he starts with the assumption that it 
is too easy to require any attention, and second, that he 
is too easily satisfied with a very indifferent job. Curves 
having curious “humps” may be termed freaks and are 
seldom, if ever, encountered in Mechanics. 

It is difficult to recommend any curve or even several 
curves as being even approximately universal, so no such 
advice will be attempted. A great number of such curves 
are listed in all instrument catalogs and special require¬ 
ments will have to be depended upon in any selection. 
However, two curves have found much favor among stu¬ 
dents and are recommended for general use. One of 


62 


MECHANICAL DRAFTING. 






















































ORTHOGRAPHIC PROJECTION. 


63 


these has obtained the name of “ Banana ” curve and the 
other is the Gr. E. D. Special. 

DIMENSIONING 

(36) In dimensioning the following rules or sugges¬ 
tions should be observed: 

(a) Dimensions should read from left to right or 
up. Fig. 72. 

(b) The auxiliary lines used in dimensioning should 
not quite connect with the lines from which they lead. 
Fig. 73. 

(c) Series. A series of dimensions should be given 
on one continuous dimension line as in Fig. 74, and not 
as in Fig. 75. 

(d) An overall dimension should always accompany 
a series, both as a check and for the convenience of the 
workman. Fig. 74. 

(e) Diameters. Diameters should be placed on a 
linear diameter of the circle or as in Fig. 76 whenever 
possible; when necessary to indicate the diameter on a 
straight line projection of a circle, the dimension should 
be accompanied by the letter D. Fig. 77. 

(f) Do not place dimensions on or along Center 
Lines. Fig. 78. 

(g) Inasmuch as the meaning of hidden lines is not 
always clear, it is had practice to place dimensions on 
such lines. 

(h) Leaders. All leaders, Fig. 79, should he made 
mechanically and not freehand. 

(j) Arrows. To lessen the difficulties of the begin¬ 
ner in making good arrowheads, the method shown in 
Fig. 80 is recommended. The arrows are both simple in 


64 


MECHANICAL, DRAFTING. 




















orthographic projection. 


65 . 












66 


MECHANICAL DRAFTING, 




















ORTHOGRAPHIC PROJECTION. 


67 













68 


MECHANICAL, DRAFTING 






.... .... . ' 




REAMERS 











































orthographic projection. 


69 


construction and look well. The arrows of dimension 
lines contain two barbs , while those of leaders , Fig. 79, 
but one. 

(k) Notes. For explanatory notes the leader should 
end so that the notes may read either horizontally or 
vertically as the dimensions, but not diagonally. Fig. 79. 

(l) Dimensions up to two feet should be stated in 
inches; e. g., 12", 18", etc. 

Two feet may be written either as 24" or 2'-0". 

Except for sheet metal, dimensions above two feet 
should be expressed as follows: 2'-3", 6'-4", 7'-0", etc. 

The dimensions for sheet metal should be given in 
inches and in the order of thickness, width, length; 
e. g., %" x 36 x 120. 

SHOP TERMS 

(37) Drill. Quite frequently instead of indicating 
the diameter of a hole on the drawing according to the 
suggestions under Diameters in Dimensioning , it is found 
convenient to substitute a note which gives at the same 
time the diameter of the hole and the shop operation 
necessary in making that hole. Eound holes up to l 1 ^" 
or D/ 2 " in diameter are ordinarily cut with twist drills 
such as are shown in Fig. 81. In such cases the note that 
will be substituted for the diameter is (%" Drill, 1" Drill, 
etc.). Such drilling operations can be done on a Lathe, 
tho more conveniently and rapidly on any of the types of 
Drill Presses shown in Fig. 82. 

(38) Fillet. It is a well recognized principle of 
mechanics that a break is much more likely to occur in 
sharp corners of a machine than elsewhere, the corner 
seeming to furnish a starting point for the break. For 
this reason and others which need not be mentioned, all 
corners found on castings are seen to be slightly rounded, 


70 


MECHANICAL, DRAFTING. 









































ORTHOGRAPHIC PROJECTION. 


71 


Fig. 83. This rounded corner is known as a fillet; like¬ 
wise the material which is used to make this fillet in pat¬ 
terns takes the same name. In Fig. 84 is shown the 
method of making such filleted corners in patterns. The 
triangular piece shown is made of wood, shaped by driv¬ 
ing thru a Die, Fig. 85, as dowel pins, or of hard wax 
rounded by a heated rod, Fig. 86, or it may be of leather 
which can be purchased in coils of any length. The 
leather fillets, of course, are most convenient for very 
irregularly shaped pieces. The radius of the arc of such 
fillets is quite generally Vi"; however, it is necessarily a 
matter of machine design and for very large pieces the 
radius must be greater than 

(39) Conventional Lines. The conventional lines 
shown in Fig. 87, are standard and should be followed 
strictly. Concerning the hidden lines , it may be said that 

no one thing except dimensions will add to or detract 
from the appearance of a drawing more than care or lack 
of it in the correct drawing of hidden lines, both as to the 
uniform length of the dashes and uniform space between 
dashes. In tracing, follow strictly the weights given in 
the figure for these various conventional lines. 

(40) Order of inking in tracing. In tracing, the 
following order should be observed for most rapid and 
accurate work, Fig. 88. 

1. Large circles and arcs. 

2. Small circles and arcs with the bow pen. 

3. Irregular curves with special curve. 

4. Horizontal lines with the T-square. 

5. Vertical lines with T-square and triangles. 

6. Inclined lines in groups, e.g., 30°, 45°, and 60°. 

7. Other oblique lines. 

8. Dimension and auxiliary lines. 

9. Section lining, dimensions and notes. 


MECHANICAL DRAFTING. 


EJoa r-d 



Fig. 89 



Fig. 90 















ORTHOGRAPHIC PROJECTION. 


73 


TRACING CLOTH 

(41) Tracing cloth is a medium quality of linen 
coated with a preparation which gives it a smooth hard 
surface and renders it transparent. Of the various 
grades of cloth on the market, the imported brand “Im¬ 
perial” gives by far the greatest satisfaction and is 
recommended for general use. Always before making 
use of any piece of cloth be sure to rip off about of 
the selvage edge; it may prevent a bad buckling of the 
tracing. 

Tacking to the board. It is best always to have the 
sheet of tracing cloth slightly larger than the sheet of 
paper so that the tacks used in pinning down the cloth 
may be placed outside the sheet. In tacking down the 
cloth, preferably always with the dull side up, be sure to 
stretch very tight and tack firmly. See Fig. 89 for best 
order of tacking. 

Preparation of the surface of the cloth. Unless pre¬ 
pared in some way, the surface of the tracing cloth will 
likely take the ink very poorly, giving ragged and faded 
out lines. The cloth may be dusted or rubbed with chalk 
or preferably (magnesium carbonate), which may be 
purchased at any drug* store in 5-cent blocks, and then 
rubbed with a piece of linen. A draftsman may find it 
much to his advantage to have in his kit for the dusting 
of the surface of the cloth, a new (wool felt) blackboard 
eraser, Fig. 90. If kept full of chalk or magnesium dust, 
the eraser gives most excellent results. 

Order of work. Unless one is sure of being able to 
finish the tracing of several views of a drawing before it 
is necessary to stop work, it will be found best always to 
trace one view at a time, finishing that view before leav- 


74 


MECHANICAL, DRAFTING. 









ORTHOGRAPHIC PROJECTION. 


75 


ing work. Tracing cloth has a decided tendency to 
stretch and warp, and it may be found most difficult to 
make old lines check with new if the tracing has been left 
standing for a day or more. 

Erasing. In erasing, use the pencil eraser always in 
preference to the ink eraser or knife. It may require 
more time to erase a mistake; however, the cloth will be 
found in good condition after such erasing; while the ink 
eraser or knife quite easily roughens the surface and 
causes blots on application of new ink. A knife may be 
used to advantage in scraping out slight accidental exten¬ 
sions of lines , Fig. 91. 

Caution. If necessary to rule across ink lines, be 
sure to move the pen rapidly. If the pen is moving 
slowly the ink will likely follow down the old ink line to 
the T-square or triangle and cause a bad blot. 

Weights of lines. It will be necessary to use but two 
weights of lines thruout the work in tracing. A number 3 
line, slightly less than 1/32" for all outlines, both hidden 
and visible, and a number 1/2 line (a very thin line line) 
for all dimension, auxiliary, section, and center lines. 

BEVELLEH AND RAISED TRACING RULES 

For tracing the two rulers shown in Figs. 91a and 
91b are indispensable. With the bevelled ruler, Fig. 
91a, it is possible to rule across inked lines without any 
danger of blotting. The raised ruler of Fig. 91b saves 
an immense amount of time, as it makes it possible to 
continue tracing no matter how many ink lines are still 
wet. 

SCALE 

(42) In using the ordinary architect’s scale, which 
has been designed to make drawings of such size that 


76 


MECHANICAL, DRAFTING. 


etc., on the drawing is eqnal to V on the 
object, the beginner may experience some difficulty if he 
is attempting to make a drawing to the scale of %", %" 
or 1", etc., to the inch. On inspection of the scale it is 
found that for each scale the %", %", etc., at the end is 
subdivided into four parts, and each of these is further 
subdivided into three, six, or twelve parts. One of the 
four parts represents one-fourth of an inch. 

The following table may be of service to the beginner 
in obtaining from the various scales the dimensions most 
frequently used. 

Scale of 1%" to 1" from the 1 y 2 scale. 

1/4" equals space from 0 to 3. 

1/8" “ 1/2 space from 0 to 3. 

1/16" “ 3 of smallest divisions. 

1/32" “ 1 y 2 smallest division. 

Scale of 1" to 1" from 1" scale. 

1/4" equals space from 0 to 3. 

1/8" “ 6 of smallest divisions. 

1/16" “ 3 of smallest divisions. 

1/32" “ iy 2 smallest division. 

Scale 3/4" to 1" from 3/4 scale. 

1/4" equals space from 0 to 3. 

1/8" “ 3 of smallest divisions. 

1/16" “ 1 y 2 smallest division. 

1/32" “ iy 2 smallest division on 3/16 scale. 

Scale of 1/2" to 1" from 1/2 scale. 

1/4" equals 1 of four largest divisions. 

1/8" “ 3 of smallest divisions. 

1/16" “ iy 2 smallest division. 


orthographic projection. 


77 



Fig. 94 

















78 


MECHANICAL DRAFTING. 


A mechanical engineer’s scale has recently been put 
on the market. Mechanical draftsmen will find it much 
to their advantage to own one of these. 

(43) Use and construction of the stuffing box. One 

of the few uses of the type of stuffing box used in the 
drawing plate of this week is shown in Fig. 94. The 
stuffing box complete is composed of six parts: Body, 
gland, two stud bolts, two nuts. As seen, the body is 
bolted to the end of the engine cylinder, the piston rod 
passing thru both the body and the gland. Around the 
piston and between the gland and the shoulder of the 
body is shown the packing (hemp or especially prepared 
packing) which , when the gland is drawn down tight by 
the two nuts, is jammed tight around the piston, pre¬ 
venting the escape of steam from that end of the cylinder. 



Fig. 95 











U. S. S. THREADS. 


79 


LESSON 5 
TJ. S. S. THREADS 

(44) True representation. To represent threads 
exactly as they appear on a threaded rod or bolt or in 
a threaded hole would be a very tedious process, for the 
sharp edge of the thread constitutes what is known in 
mathematics as the spiral and in this case of so slight 
curvature as to make exact construction most tedious. 
Hence, in the original attempt to simplify the construc¬ 
tion in drawing such threads, straight lines were substi¬ 
tuted for these curved spiral lines and threads were 
represented as shown in Fig. 95, for threads on a bolt, 
and as in Fig. 96, for threads in a threaded hole. In 
each of these cases the notched edges represent the 
threads as they actually appear in profile. 

Crest, root, outside diameter, root diameter, pitch. 

The sharp edge of the thread is known as the crest, Fig. 
95, the depression line as the root. The diameter of the 
crest of the thread is known as the outside diameter or 
the diameter of the bolt. The diameter of the root is 
known as the root diameter or diameter of the tapping 
drill. 

For holts and screws of various sizes the size of the 
thread, hence, the number of threads per linear inch 
must vary. For each sized screw there is a standard 
thread which is indicated by the term pitch. This term 
pitch may mean either the number of threads per linear 
inch, Fig. 95 (B in this case equals 8, including 7 full 
threads and two half threads) or, the distance in inches, 
either fractional or decimal, between two consecutive 


80 


MECHANICAL, DRAFTING. 




Fig. 98 


Fig. 97 



Fig. 99 



Fig. 100 


Fig. 101 














































U. S. S. THREADS. 


81 


thread crests or the width of one thread, as indicated by 
B, Fig. 95. 

Conventional representation. Inasmuch as in making 
a drawing there is ordinarily no necessity for the drafts¬ 
man to go to the extra trouble to represent bolt threads 
as shown in Fig. 95, the conventional representation, 
shown in Figs. 96, 97 and 98, has been devised and is 
universally used. In this conventional representation it 
is seen that the light inclined lines represent the crest of 
the thread while the short heavy lines between represent 
the roots of the threads, the notches at the right and left 
having been omitted. 

Slope of thread. In passing around a right-hand 
threaded bolt, Fig. 99, moving in a clockwise direction 
from point d to e, the moving point has advanced along 
the axis of the bolt in a direction shown by the arrow 
and has moved in this direction one-half the width of one 
thread, or % B. Hence, in representing threads on the 
front of a threaded holt, the direction of the slope of the 
lines representing the crests and roots of the thread must 
be from left to right up in the direction of the axis of 
the bolt, Fig. 100. 

In moving from point e in a clockwise direction, to 
the point f, the moving point has advanced along the 
axis in the direction shown by the arrow, a distance equal 
to one-half the width of one thread or % B. Hence, in 
representing the thread in the back of a threaded hole, 
the lines representing the crests and roots must slope 
from right to left up in the direction of the axis, Fig. 101. 

Shop note. The following note may be used to indi¬ 
cate the outside diameter of the thread and the pitch or 
number of threads per inch for any threaded hole on a 



MECHANICAL, DRAFTING. 









Use-*em-up” Drill Socket 











U. S. S. THREADS. 


83 


piece of machinery (%"xlO pi.), pi. being the abbrevia¬ 
tion for pitch. 

(45) Tapping drill. The dimension C, Fig. 95, gives 
at once both the root diameter of the threads, and the 
diameter of the tapping drill or twist drill that would be 
used in drilling a hole to be threaded to accommodate 
the screws. It is seen that this dimension C, the diameter 
of the tapping drill, gives the distance between the two 
parallel lines which limit the notches of the thread. 

SCALES 

(46) Architect’s scale. The inches on the archi¬ 
tect’s scale are divided into halves, quarters, etc., i. e., 
into divisions which are multiples of two, making it pos¬ 
sible to draw, without any interpolation, plans, etc., of 
objects whose dimensions are given in feet and inches. 

Engineer’s scale. On the engineer’s scale the inches 
are divided into various numbers of subdivisions, these 
numbers being multiples of ten; i. e., the inches are 
divided into 10, 20, 30, 40, 50, or 60 divisions. By use of 
this scale without any interpolation maps may be made 
and drawings plotted directly from field notes in which 
the distances are all given in feet and tenths of feet. 

Scale versus size. A drawing made to such a size 
that one-half inch on the drawing equals one foot on the 
object drawn, is said to be made to one-half scale. How¬ 
ever, if the drawing be made so that one-half inch on the 
drawing represents one inch on the object the drawing is 
said to be made one-half size or to a scale of y 2 " to 1". 


84 


MECHANICAL DRAETING. 



~i 


\ 






/ / 

/ 

/ 

/ 

/ 

Top 





1 

1 

Front I 

1 1 
|sioe | 

1 1 

1 1 








Fig. 102 




Fig. 105 Fig. 104 























































































































































u. s. s. Threads. 


85 


POSITIONS OF THE THIRD AND FOURTH VIEWS OF A 
WORKING DRAWING 

(47) In Fig. 102 is shown the correct arrangement, 
orthographicaly, of the three views of a working draw¬ 
ing. However, occasions may arise in which it will be 
inconvenient to place the side view directly opposite the 
f ront ; in this case we may imagine that the line of inter¬ 
section of the end plane and the horizontal plane becomes 
an axis about which the end plane is revolved, Fig. 103, 
until it coincides with the horizontal plane. This entire 
horizontal plane is then revolved about its line of inter¬ 
section with V as an axis, until it coincides with V. The 
side view will now be found opposite the top instead of 
the front. If two side views are necessary to show the 
construction they may be placed on either side of the 
front view, Fig. 104, or on either side of the top view, 
Fig. 105. No other arrangement is permissible. 

In constructing a three view working drawing it is 
best always to construct the top and front views from 
dimensions and by projection ; then, to obtain the side 
views from these two, entirely by construction and not 
by the use of dimensions. For the sake of construction 
the two ground lines, Fig. 102, may be drawn in lightly; 
however, they should be erased when no longer needed. 

SHOP TERMS 

(48) Tapping drill. A tapping drill is a twist drill 
of the common type, named a tapping drill in this case 
because it has been used in drilling a hole which is to be 
threaded to receive a screw. 

Tap. A tap is an instrument, somewhat resembling 
a bolt, that is used in cutting threads in any drilled hole. 


86 


MECHANICAL, DRAFTING. 


Starter or Toper Tap 




Finishing or BoTtoming 



Fig. 106 



Fig.108 

































U. S. s. THREADS. 


87 


A tap is made by first threading a rod of tool steel as tho 
it were to be made into a bolt, then grooves are cut or 
milled lengthwise thru these threads, Fig. 106; on the 
ordinary type of tap four such grooves are milled, pro¬ 
ducing four cutting edges. These grooves likewise fur¬ 
nish space in which the chips or shavings may collect. 
Taps ordinarily come in sets of three, Fig. 106, the one 
known as a starter being ground down on the end to per¬ 
mit it to start easily in the hole. The medium tap, ground 
down only slightly on the end, finishes the thread nearly 
to the bottom of the hole, while the finishing or bottom 
tap is used to finish the thread entirely to the end of 
the hole. 

Finish. To indicate that any surface of a piece of 
machinery is to be finished or machined on a lathe, 
shaper, or planer, the letter “f” is used, Fig. 107. If 
this letter “f” is omitted on a drawing the workman will 
understand that a certain surface or surfaces are to be 
left rough, if the piece is a casting or forging. 

FACE PLATE 

(49) Chucks versus face plate. In Fig. 123, which 
is of a common lathe, is shown a piece of material held 
in place by the four jaws of what is known as a chuck. 
It is seen that these jaws are placed in pairs and are run 
in and out by means of a screw turned by a key. This 
chuck can be used to hold all pieces of material of a regu¬ 
lar shape and convenient size; however, occasion fre¬ 
quently arises in which it cannot be used. In such cases 
a plate known as a face plate, Fig. 109, is screwed on the 
end of the shaft of the lathe in place of the chuck. The 
piece of material is then suspended between the two cen¬ 
ters indicated, and caused to revolve with the face plate 


88 


MECHANICAL, DRAFTING 


























U. S. S. THREADS 


89 











90 


MECHANICAL DRAFTING 














































U. S. S. THREADS. 


91 


by means of various kinds of clamps, Fig. 110. The 
piece of material may likewise be clamped to the face of 
the plate by bolts and plates, the heads of the bolts being 
slipped down into the T grooves seen in the rim, Fig. 111. 

(50) Boring bar. For outside turning on a lathe the 
ordinary type of cutting tool is used, Fig. 112. However, 
for inside cutting or boring a tool known as a boring tool 
is used and if the piece to be bored is a cylinder of any 
length the tool is held by a bar known as a boring bar, 
Fig. 113. 



Fig. 110 










92 


MECHANICAL, DRAFTING. 








u. s. s. threads 


93 


















94 


MECHANICAL DRAFTING. 



3rs3a-' " 

SRiUtO. 


mmmmm 


US' vtft 

L J 




U. S. S. THREADS 


95 





















MECHANICAL DRAFTING. 
















SHOP TKRMS. 


97 


LESSON 6 

SHOP TERMS 

(51) Mill. In the shop operation required in cut¬ 
ting slots, grooves known as key seats, also other simi¬ 
lar operations, Fig. 114, a machine known as a milling 
machine is used. The cutting tools resemble the common 
type of circular saw and operate on the same principle. 
As seen in Fig. 115, which is of a horizontal milling 
machine, the cutter is fastened rigidly to the revolving 
shaft or arbor while the piece of material to he machined 
is clamped to the table and the table moved either by 
hand or automatically slowly under the cutter, as a log 
is fed into the saw of a sawmill. For special work mill¬ 
ing cutters of many odd designs are made, as seen in Fig. 
116. The machine shown in Fig. 117 is known as a ver¬ 
tical milling machine, the shaft or arbor in this case being 
vertical. To prevent vibration in the arbor of the hori¬ 
zontal machine (this vibration being known as. chatter) 
and consequent rough work of the cutter, chatter braces, 
shown in Fig. 115, are being put on most machines of late 
design. The note used to indicate any desired milling 
operation may he as follows: “2" mill”; the two inches 
indicating the diameter of the milling cutter; or “mill 
%" key seat, 4" long,” “Mill %" slot, deep,” etc. 

Tap. In cutting standard threads in nuts or holes 
which are to receive machine or cap screws, the 
threading tool, known as a tap, Fig. 106, is used. The 
note that will be used in this connection is %" tap, %" 
tap, etc., or %"xl2 pi. tap. The %" or %" dimension in 
either case gives the outside diameter of the thread and 





98 


MECHANICAL DRAFTING 



Planei 














SHOP TERMS. 


99 



> 









100 


MECHANICAL DRAFTING. 
































































































SHOP TERMS. 


101 


the pitch is to be understood as U. S. Standard; if not 
standard, the pitch is to be indicated by the 12 pi., etc., 
as in the second example. 

Bore. In all cases where a round hole is to be 
machined and the hole is either so large that a twist drill 
cannot be used or it is desired to give such a finish to the 
hole as is impossible in the inevitably somewhat rough 
work of the twist drill, the work will be done ,on a lathe 
by means of the short boring tools or by cutting tools in 
connection with the boring bar and the operation will be 
termed boring instead of drilling. The note referring to 
such an operation is 7" bore, etc., the dimension referring 
to the diameter of the hole. Such boring operations 
are ordinarily necessary on holes whose diameters are 
greater than two inches. Twist drills larger than two 
inches in diameter are not in very common use as it 
requires an extremely heavy drill press to operate them 
satisfactorily. 

SECTIONING 

(52) Solid cylinders. The draftsman should keep 
in mind the fact that there is but one thing to be gained 
in sectioning, i. e., to show more clearly the interior con¬ 
struction of any piece of machinery; if the section does 
not accomplish this purpose it is just so much wasted 
labor. This point refers particularly to solid cylinders, 
e. g., shafts, bolts, screws, etc., Fig. 118, which should 
never be sectioned. 

Interpolated or revolved sections. In such cases as 
are shown in Fig. 119, with respect to rims and spokes 
of wheels, standard construction iron, etc., sections 
known as interpolated or revolved sections are given to 
show the cross-section of the material at certain places. 


102 


MECHANICAL, DRAFTING. 





Fig. 121 





Carriage * Boir 



Square-Head Machine- 
Boir 









































































SHOP TERMS. 


103 


It is a rule that even when a second view of a wheel is 
given the spoke is not to be sectioned while the rim and 
hub may be if desired, and the shape of the spoke given 
by two interpolated sections as shown. 

Section lines. Indication of material by variation in 
section lines. It is the custom in many shops to indicate 
the material of which a piece of machinery is to be made 
by using a characteristic section line for any parts of 
that piece which have been sectioned, Fig. 120. There 
are some apparent disadvantages in this, however, for 
there is at present no universal standard system of sec¬ 
tion lining. Some shops use one characteristic for brass, 
wrought iron, etc., and others a radically different char¬ 
acteristic. Furthermore, unless one uses these section 
lines constantly or has a chart of them with him always, 
he may find it quite difficult to remember some of them. 
A third objection is that it requires an excessive amount 
of time to draw some of these section lines. 

Indication of materials by abbreviations and univer¬ 
sal section lines. For greatest convenience and ease, 
both in making and reading a drawing, the writers 
approve the universal section lining with material abbre¬ 
viations as a substitute for the above system, i. e., the 
use of the standard section line now used for cast iron 
as the standard for all materials and the particular mate¬ 
rial of which the piece is to be made indicated by its 
characteristic abbreviation as shown in Fig. 120a. These 
abbreviations are easy to remember and the section lines 
can be drawn rapidly. 

THREADS 

(53) Standard conventions. Both conventional 
methods of indicating U. S. S. threads, as shown in Fig. 
121, are standard and may he used as preferred. 


104 


MECHANICAL DRAFTING. 



Fig. 123 













Horizontal Return Fire-Tube 

Boiler 


105 


SHOP TERMS. 



Fig. 124- 















106 


MECHANICAL DRAETING 























SHOP T£RMS. 


107 


Hidden threads. In representing hidden threads in a 
threaded hold, Fig. 122, the slope of the broken lines is 
the same as that of lines representing threads on the 
front of a threaded bolt. 

FLUE HOLE CUTTER 

(54) Process of construction. The flue hole cutter 
used in the drawing plate of this week is composed of 
two main parts, shank and tool holder. The shank is 
made from a bar of machine or cold rolled steel, the long 
taper being turned down on a lathe and the threaded end 
turned down and the threads chased on a lathe. The two 
flats on the upper end are cut on a milling machine and 
the hole in the lower end drilled in a lathe, the shank 
being held in the chuck and the drill in place by the cen¬ 
ter of the tail stock, Fig. 123. The tool holder is forged 
from a block of tool steel (tool steel being used because 
of excessive strain which the holder must stand). The 
large round and two small holes were drilled on a drill 
press and threads cut with a tap. The irregular hole 
was first forged out roughly and then shaped up on a 
shaper or filed up by hand. 

Use. There are in general use two types of boilers. 
In the one known as fire tube the water is on the outside 
of the tubes, and heated gases and fire pass thru the 
tubes . In the other, which is known as the water tube 
boiler, the water is on the inside of the tube and the fire 
and heated gases on the outside, Fig. 124. The flue hole 
cutter mentioned above is used in cutting the holes in the 
heads or tube sheets for the tubes of the fire tube type 
of boiler. Holes %" in diameter are first drilled in the 
tube sheets for the center or guide pin of the cutter Fig. 
125; the tool having only one cutter requires this center 
pin to hold it rigidly in place. See Fig. 125 for operation 
of cutter. 


108 


MECHANICAL DRAFTING. 


Radial Drill 




Fig. 126 













































STANDARD BOUTS AND NUTS. 


109 


LESSON 7 

STANDARD BOLTS AND NUTS 

(55) Bolts and nuts. A bolt may be broadly defined 
as a round rod of iron or steel, having a head on one end 
and threaded on the other to receive a nut. 

There are in use at present two distinct classes of 
bolts, named from their distinctive uses, the one class 
called machine bolts and the other carriage bolts. 

It is rather difficult to define the term machine bolt 
because of the many shapes such bolts may have and the 
number of uses made of them. However, a carriage bolt 
may be easily defined as a bolt which has an oval head 
and whose shank is squared for a distance of from %" 
to %" just under the head; the side of this square being 
about the same as the diameter of the remainder of the 
bolt. This bolt is used in wood work and when drawn 
into a hole the square under the head takes a grip on the 
wood which prevents turning of the bolt when the nut is 
drawn. The head being oval and very thin draws down 
well, leaving very little metal projecting. The bolt will 
be understood from inspection of Fig. 126. 

(56) Process of manufacture. The process of manu¬ 
facture of both general classes of bolts is the same. 
Rods of iron or steel are cut into pieces of some definite 
lengths, according to length of bolt desired. These pieces, 
heated at one end in a furnace, are placed one by one 
between the two jaws of a machine called a bolt header, 
leaving a certain length of the heated end projecting, and 
the ram of the machine is brought against this heated 


U.S.S. Bolts <5c Screws 


110 


MECHANICAL DRAFTING. 






Fig. 127 













































































































































































































standard bouts and nuts. 


Ill 


end with sufficient force to mash and form the heated 
metal into the desired shaped head. The other end is 
afterwards threaded in a threading machine. The 
threading tool, called a die, is made of tool steel, and 
resembles somewhat an ordinary nut used on these same 
bolts. 

The nuts for the bolts are either punched from sheets 
of metal of the proper thickness or cut from steel bars 
of the proper shape. The ordinary cheap grade of nuts 
is punched from a sheet of metal, a round hole punched 
thru the center and this hole afterwards threaded with 
a tap. Better grades of nuts, usually hexagonal, are cut 
from hexagonal bars. Holes are punched or drilled in 
these pieces and these holes threaded as explained above. 

(57) Machine bolts. Machine bolts are divided into 
a number of classes, each class being named either from 
its peculiar shape or its distinctive use. The dimensions 
of the several parts of all such bolts have been standard¬ 
ized, tables arranged, and the construction and size of 
every part of any particular size bolt is perfectly definite. 

(58) Hexagonal and square-headed bolts. Inas¬ 
much as these two classes of bolts are usually dealt with 
in the same table of dimensions, it will perhaps be as well 
to include both in this discussion. In Fig. 127 is shown 
the conventional manner of representing hexagonal and 
square-head bolts in a mechanical drawing. It will be 
noticed that the hexagonal bolt is so placed that three 
faces of both the bolt head and the nut are visible and 
the square head bolt is so placed that two of its faces are 
visible. This placing should be strictly adhered to, espe¬ 
cially in machine sketching where it may be necessary to 
show the kind of bolt by only one view. 


112 


MECHANICAL DRAFTING. 


Likewise it will be seen that on both bolts the outer 
corners of the heads and nnts have been ground or turned 
oft until the face of the head and nut is a circle tangent 
to the hexagonal or square limits of the head or nut. 
This bevel on the head or nut is called the chamfer of 
the head, etc. 

In constructing the end view of any bolt the chamfer 
circle is first drawn (the diameter of this chamfer circle 
will be found in table under head of (( Distances Across 
Flats” or et Short Diameter”) and the hexagon or square 
circumscribed by means of the 30°x60° or 45° triangles. 
No other method should be used for obtaining the hex¬ 
agon or square. 

The length of such bolts is.always the distance from 
the end of the bolt to the under surface of the head. 

For each different diameter of bolt a standard thread 
has been selected and named according to number of 
threads per linear inch; e. g., on a standard %" bolt will 
be found 11 threads per inch. The number of threads 
per inch is usually spoken of as pitch; e. g., 11 pitch 
means 11 threads per inch; the word pitch is usually 
abbreviated to pi., and a bolt may be explained by some 
such note as %"xlO pi., meaning a bolt %" in diameter, 
having 10 threads per inch. 

In listing such bolts in a Bill of Materials, the follow¬ 
ing order should be used: 1x8x4, Fin. Hex. Bolt. This 
indicates a finished hexagonal 1" bolt, 4" long, 8 threads 
per inch or 8 pitch. 

The geometrical construction indicated in Fig. 127 is 
the conventional construction and should be followed 
carefully. 


STANDARD BOI/TS AND NUTS. 


113 


(59) Cap-screws. Cap-screws, both hexagonal and 
square, are intended for fasteners; e. g., to hold a cylin¬ 
der head to the cylinder, etc., in which case the screw 
passes thru a hole in the cylinder head and screws into a 
threaded hole in the cylinder. However, the cylinder is 
mentioned merely by way of illustration, stud bolts being 
mostly used in this particular way, acting partially as 
guides in assembling. Fig. 127. 

All cap-screws of 1" and less in diameter and 4" long 
and under, are threaded three-fourths of their length; 
when longer than 4", they are threaded one-half length. 
They should be listed in Bill of Materials as follows: 

— 12xiy 2 "Hex. Hd. Cap-Screw. 

The geometrical construction for these screws will be 
found on sheet of Bolts and Nuts, Fig 127. 

(60) Set-screws. Set-screws are named from their 
use and further divided into different kinds of set screws 
according to the shape of the point or head. All set¬ 
screws may be classed as fasteners, being used to clamp 
or hold one piece of machinery in a definite position with 
respect to another; e. g., to hold a pulley rigidly to a 
shaft, etc. Such screws are either made of tool steel, oil 
hardened, or of machine steel or wrought iron, case hard¬ 
ened. No screw whose head exceeds the diameter of the 
body more than 1/16" should be classed as a set-screw. 

From the figure on the Bolt Sheet, Fig. 127, it will be 
seen that the length of the headless set-screw or gib- 
screw is the total length of the screw. 

Set-screws should be listed in a Bill of Materials as 
follows: %" — 12x2" Set-Screw. 

(61) Collar-screws. In many cases to prevent scar¬ 
ring from friction of the head of a cap-screw, washers 
are needed. A screw known as the collar-screw combines 


114 


MECHANICAL DRAFTING 


































STANDARD BOUTS AND NUTS. 


115 


this washer with the square head. This variety of screw 
will be found mostly on machines whose parts fit snugly 
and require only a moderate clamp, or where the screw 
is frequently being loosed and drawn. Example will be 
found on Bolt Sheet, Fig. 127. 

This screw should be listed in Bill of Materials as 
follows: y 2 " — 12x2" Sq. Hd. Collar-Screw. 

(62) Round and fillister head machine-screws. Quite 
frequently it is necessary to use screws in places in which 
it is difficult to use a wrench. For such uses screws with 
slotted heads are made and named round or fillister head 
machine-screws according to the construction of the 
head; examples may be found on Bolt Sheet, Fig. 127. 

These screws are made from bars slightly larger than 
the heads, cut to proper lengths, turned down and 
threaded in screw machine, and should be listed in Bill 
of Materials as follows: %" — 12xl%" Rd. Hd. Ma¬ 

chine-Screw. 

(63) Flat-head machine-screws. Flat-head machine- 
screws have countersunk heads and are to be used where 
it is desired to have the heads flush with the surface of 
the piece into which they are screwed. The holes into 
which such screws are drawn must be countersunk to 
receive the heads. See example on Bolt Sheet, Fig. 127. 

Such screws should be listed in a Bill of Materials as 
follows: %" — 10x2" Flat-Hd. Machine-Screw. 

(64) Stud Bolts. A stud holt is a rod of iron or 
steel threaded on both ends. It is used largely as in the 
case of cylinder heads where it is desired that the bolts 
shall act as guides for placing the head quickly and 
easily into position; the stud is screwed tightly into the 


116 


MECHANICAL, DRAFTING 





















































standard bouts and nuts. 


117 


cylinder and the head is drawn down with the regular 
standard nuts. See Fig. 128. 

(65) Bolt threads. If represented exactly as it ap¬ 
pears the ordinary U. S. S. thread would be shown as 
in Fig. 129. The sharp edge of the thread being known as 
the crest and the division line between the threads as the 
valley or root. The large diameter of the thread is, of 
course, the same as the diameter of the bolt. The small 
or root diameter will he found in the tables under the 
head of tapping drill. 

(66) Conventional threads. To represent a bolt with 
the notched edges, as in Fig. 129, requires an unneces¬ 
sary amount of care, and a conventional thread has been 
devised as a substitute; this is shown in Fig. 130. In 
this figure it will be seen that the notched edges are omit¬ 
ted. The light lines represent the crest of the threads 
and run entirely across the bolt, while the short heavy 
lines between these represent the roots or valleys of the 
threads, and are limited by lines whose distance apart is 
equal to the distance C or the tapping drill for that 
size bolt. 

This same convention is used to represent the threads 
in a threaded hole, Fig. 131; however, it must be noted 
that the direction of slant of the thread lines is differ¬ 
ent; i. e., for the threads on the front of a bolt ( right- 
hand thread) the lines slope from left to right up, while 
the lines for threads on the back of a bolt or a threaded 
hole slope from right to left up. Mistakes can easily be 
made in this; however, after inspection of an actual bolt 
it will be easily understood. In drawing the lines for 
conventional threads they should be given a slope of 
from 5 to 10 degrees, not more. The distance between 
the lines need not be scaled according to the pitch. The 


118 


MECHANICAL, DRAFTING. 




















































STANDARD B0L/TS AND NUTS. 


119 


number of threads per inch is invariably indicated by a 
note (e. g., %"xlO pi.) and the conventional lines may 
be spaced by the eye so as to appear symmetrical. 

(67) Square threads. For bolts which are being 
constantly loosed and drawn, as in the tail stock of a 
lathe, etc., a thread is used in which the friction does not 
increase so rapidly with the tension as in the V thread. 
This is the square thread, the bearing surfaces of the 
threads being perpendicular to the axis of the bolt. No 
conventional representation of this thread has been 
devised, so they will always be represented as in Fig. 132. 

(68) Double square threads. Whenever it is desired 
to thread a bolt or screw so that the nut or hand wheel 
will draw with the greatest speed, a double set of threads 
is used; i. e., two threads of the same pitch. Unless 
inspected closely it will appear to be only a single thread. 
This thread will be found on the screw which moves the 
center in the tail stock of a lathe. This thread is repre¬ 
sented in Fig. 133. 

BOLT AND PIPE DIES 

(69) The thread cutting tools used in cutting threads 
on bolts and pipes are known as dies. The type of die 
used in cutting bolt threads, as shown in Fig 134, is 
made from a flat plate of steel thru which a hole is first 
drilled and tapped out with a master tap; then four holes 
are drilled around this center, giving four cutting edges. 
These dies have no taper, as the outside diameter of a 
bolt should be uniform. The dies used in cutting threads 
on pipe may be either solid or in sections as one indi¬ 
vidually prefers. Both types are shown in Figs. 135 and 
136. All such dies have a standard taper of 1" in 16" so 
that any pipe threaded by one of these dies, when 


120 


ME)CHANlCAIy DRAFTING. 

















STANDARD BOUTS and nuts. 


121 


screwed into a pipe fitting, makes a water or steam tight 
joint when drawn sufficiently tight. 

KEYS AND KEYWAYS 

(70) In fastening wheels, pulleys, etc., to shafts two 
classes of fasteners may be used, set-screws or keys. 
Set-screws may be used to advantage in all cases in which 
the twisting force on the shaft is very small . It is not 
wise to use such a fastener on large pulleys or in cases in 
which the load is likely to be very great. In this latter 
case one of three varieties of key may be used according 
to the nature of the machine. These keys and keyways 
are (a) Keys on flats, Fig. 137; (b) Straight seated keys, 
Fig. 138; (c) Woodruff keys, Fig. 139. It is clearly seen 
that the first type of key has a very limited use, and owing 
to the fact that the Woodruff key is patented, the straight 
keys and seats have the most general use. In this type of 
key, it is seen, Fig. 138, that one-half of the recess is 
milled or cut into the shaft (this groove being known as a 
keyseat) while the other half of the recess is cut into the 
hub of the pulley and is known as the keyway. When 
fitted over each other they should form nearly a square, 
the height being slightly less than the width. The keys 
used in this connection are cut from square bars of cold 
rolled steel and filed to a slight taper on one side only, so 
that when driven in far enough they wedge between the 
hub and shaft, thereby preventing the pulley both from 
sliding along the shaft in either direction and from turn¬ 
ing about the shaft. 

CONVENTIONAL BREAKS 

(71) In making a drawing of a shaft of uniform 
diameter it is quite frequently impossible to represent the 


122 


MECHANICAL, DRAFTING. 








































































STANDARD BOLTS AND NUTS. 


123 


whole shaft without changing scale. As a substitute for 
this change of scale any convenient space may be used to 
represent the length of the shaft. A conventional break 
being shown at some place in this length, as in Fig. 140, 
the dimension given is for the total length of shaft. The 
same conventional break may also be used in a long tap¬ 
ered pin, the whole of which cannot he conveniently 
drawn. This form of break should be made mechanically 
while others, which may be necessary, can he drawn free¬ 
hand, Fig. 141. 

SHAFT COUPLER 

(72) The shafting used in transmitting power thru 
a shop comes in standard lengths of from 20 to 40 feet. 
Any length of shaft may be made up from these standard 
lengths by various types of shaft couplers, one of which is 
shown in Fig. 142. One-half of this coupler is keyed to 
one end of one bar of shafting and the other half to the 
adjacent end of the next bar. The use of four or six bolts 
thru the webs of these coupler parts converts these pieces 
of shafting into one double length of shaft. 

BEARINGS AND HANGERS 

(73) Hangers. Lengths of shafts are supported by 
either of two types of hanger, the one known as a wall 
hanger, the other known as a ceiling hanger. In Figs. 
143 and 144 are shown both types of hanger, the construc¬ 
tion of which needs little explanation. The two half 
boxes or casings thru which the shaft passes are lined 
with an alloy of zinc and lead, which minimizes the fric¬ 
tion and consequent loss of power in such bearings. 

Brasses. In certain types of machines it is desirable 
to use brass for bearings rather than the combination of 


124 


MECHANICAL DRAFTING. 


lead and zinc. Such bearings are ordinarily made in 
halves, constructed so as to permit of a slight adjustment, 
Fig. 145. These half bearings are commonly known as 

brasses. 

Babbit. The alloy of lead and zinc mentioned above 
is commonly known as babbit. The greater the amount of 
zinc the harder this compound is. Two of the material 
advantages of babbit for bearings are, that the metal is 
cheap, and such bearings can be easily replaced by a work¬ 
man of but ordinary experience. Babbit lining is poured 
while molten into the cast iron casings with the shaft in 
place. 


assembly drawing. 


125 


LESSON 8 

ASSEMBLY DRAWING 

(74) Definition. An assembly drawing of a machine 

is a two or three view orthographic projection of a ma¬ 
chine completely assembled; i. e. all parts in their proper 
working place. 

Uses. Assembly drawings have three important nses. 
(1) As an index to a working drawing; i. e., an assembly 
of a machine is ordinarily given with the set of detail 
working drawings to explain the nse of each of these de¬ 
tails in the machine; (2) For purposes of advertisement 
or magazine illustration; (3) As a construction guide in 
assembling machines which may be sent out from shops 
in sections. 

Characteristics. Some characteristics which may be 
noted of assembly drawings when used for any of the 
above purposes are: (a) All dimensions are ordinarily 
omitted; (b) The several views are elaborately sectioned 
to explain clearly all inside constructions; (c) When 
given with a set of details the assembly will ordinarily 
occupy a fixed relative place on the sheet, i. e., the lower 
left corner or whole left side if necessary. 

DETAIL WORKING DRAWINGS 

(75) Arrangement of set of details. In making a set 
of details a certain order of arrangement should be fol¬ 
lowed, both for appearances and ease in reading the draw¬ 
ing. As mentioned under assembly drawings, the assem¬ 
bly should occupy the left portion of the sheet. In gen- 


126 


MECHANICAL, DRAETING. 












































































































ASSEMBLY DRAWING. 


127 

























128 


MECHANICAL DRAFTING. 



Title 


Fig. 158 



Fig. 159 
























































ASSEMBLY DRAWING. 


129 


eral, the arrangement of the details on the sheet should 
be such as to suggest their direct relation in the machine 
itself; i. e., such an arrangement as is suggested by the 
relation of these parts in the assembly. It may not always 
be possible to carry out this scheme completely; however, 
in general it will be found possible so to arrange the main 
details. For further explanation see Fig. 155. The as¬ 
sembly is here shown to the left, followed along the bot¬ 
tom of the sheet by the main detail, the remaining details 
being arranged about the sheet properly with relation to 
each other if not to the main details. 

Order of work in a set of details. In making a set of 
details, e. g., of the shaft bearing, Fig. 156, the following 
order of work will be found to lend to the greatest speed: 
(a) Sketch roughly on a piece of scratch paper, rectangles 
for the various details in their proper arrangement, Fig. 
157. (b) Enlarge upon the first rough sketch by placing 

on a second sheet of scrap paper rough rectangles for 
the necessary views of the details as they have been ar¬ 
ranged on the first sheet, Fig. 158. (c) Block out roughly 
on the sheet on which the drawing is to be placed, using 
the scale only approximately, rectangles to correspond 
to the arrangement on sheet No. 8, Fig. 159. (d) Place 

in accurately the final rectangles by means of the scale 
and draw center lines of these rectangles for the center 
lines of the various views of the details, Fig. 159. 

VALVES 

(76) There are in general use at present valves of 
two distinct designs; most of us may be familiar with the 
appearance of both of these designs but hardly with the 
construction and uses. These two types are Globe and 
Gate valves. 


130 


MECHANICAL DRAFTING. 



DISC 

lder 


. DISC 
LDER 


NELSON VA| 


Huxley Seat 
Fig. 162 







ASSEMBLY drawing. 


131 


(77) Globe valves. In Fig. 160 is shown the common 
type of Globe Valve, so named from the shape of the main 
part of the body. In Fig. 161 is given a section of this 
valve showing clearly its construction and the name of 
each part. The steam, air, or water enters at the left, 
passes np thru the opening within the rim of the seat and 
on ont to the right. When the stem is screwed down by 
the hand wheel the disc is wedged tight into the seat, 
thereby closing the opening and stopping the passage 
thru the valve. To prevent the pressure from forcing 
the contents out of the top of the valve around the stem, 
hemp or especially prepared packing is placed in the bon¬ 
net, about the stem and just under the gland, and the 
gland nut drawn down until packing is sufficiently tight 
to prevent escape. 

Discs and seats. In Fig. 162 is shown the patented 
Huxley seat now used in Nelson globe valves, also various 
types of discs used for various purposes. The reason for 
the use of the Huxley seat is that the grit that may he 
carried thru the pipes by water and steam rapidly cuts 
out the seat, making it necessary to regrind it frequently 
to keep the valve in perfect condition. These patented 
seats being made of copper, which is comparatively soft, 
keep in good shape for quite a time from the occasional 
pressure of the disc, and when worn badly may be easily 
replaced. Valve disc No. 1 is of solid brass and is quite 
common on valves. Disc No. 2 is of brass and has a re¬ 
cess in the bottom into which may be fitted a hard rubber 
or lead disc for use on air or water lines. Disc holder 
No. 3 is fitted wfith a copper ring or disc for use on 
steam lines. 

Bonnets. In Fig. 163 is shown the coupler type of 
bonnet which screws directly to the body. To regrind 


132 


MECHANICAL, DRAFTING. 




























ASSEMBLY DRAWING. 


133 


the valve seat it is necessary to remove this bonnet; 
hence, to prevent sticking of the bonnet and trouble in 
removing, no packing is used at the point indicated; a 
brass tight joint is depended upon. However, in spite of 
good workmanship, water and steam may force limestone 
and dirt out under the bonnet, causing it to stick quite 
badly. If much force is necessary to remove the bonnet 
the body may be badly twisted and the valve ruined. To 
eliminate these troubles the union type of bonnet, shown 
in Fig. 164, has been designed and finds great favor. In 
this type the bonnet does not turn as the union nut is 
run down, so that packing may be used if desired without 
the danger of bad sticking. 

Angle valve. In Fig. 165 is shown a type of globe 
valve known from its design as an angle valve; the water 
or steam enters and leaves as indicated. The internal 
construction of the valve is similar to that of the straight 
type of globe valve. 

Objection to globe valves. It is easily understood that 
especially in water lines any obstruction which may be 
placed within the pipe has a tendency to reduce the pres¬ 
sure of the water when in motion, and the pressure is 
usually an item of considerable importance. Any angu¬ 
lar turns about which the water must move reduce the 
pressure by friction, and direct obstructions reduce the 
pressure by bach currents. As the water passes thru the 
globe valve, Fig. 166, pressure is reduced in both of these 
ways; the water must make two right angular turns in 
passing thru the valve; furthermore, as it strikes the 
diaphragm a return current is created, subtracting just 
so much from the pressure. For these reasons the gate 
valve, which permits a straight passage of fluid when 
open, is considerably more efficient for water lines. 


134 


MECHANICAL DRAFTING. 










ASSEMBLY DRAWING. 


135 



Stem 


Gland 
Gland Nut 

5-t-Ljffincj Box 

Bonnet 


Disc 


Bodjy 


Seat 


Fig. 167 











136 


mechanical drafting 




4 i5 /> 


Fig. 168 


16 


Pig. 169 
















assembly drawing. 


137 



Fig. I6S 























138 


MECHANICAL, DRAFTING. 










assembly drawing 


139 



Body 




Fig. 176 


^\Secrt 


Bonnet 


Disc 






















140 


MECHANICAL, DRAFTING. 




Fig. 177 


Disc 


BocJy 


Sear 


Bonner 


Body 


Fig. 170 


DISC 




































ASSEMBLY drawing. 


141 




Seat* 


Bonnet- 


Fig. 179 


Disc 













142 


MECHANICAL, DRAFTING. 


(78) Gate valves. In Fig. 167 is shown the construc¬ 
tion and names of the various parts of the gate valve. 
The original design of gate valve contained a solid wedge 
disc, Fig. 168, which proved under various tests rather 
unsatisfactory; e. g., if the body were strained, this strain 
ordinarily developed as shown in Fig. 169, thereby open¬ 
ing up the seats and ruining the valve. Furthermore, 
when put to the test as shown in Fig. 170, the solid 
wedged disc being pushed in place by hand, it was found 
that the opening in the seat was by no means closed. The 
double wedge type was then designed as a substitute and 
was found to stand all the above tests satisfactorily, as 
shown in Figs. 171 and 172. It was also found that even 
when it is impossible to close the opening thru the one 
seat, on account of an obstruction, Fig. 173, the other side 
of the valve closes perfectly. In Fig. 174 is shown one 
design of the connection of the stem with the two discs, 
and in Fig. 175 is shown the copper facing of a disc as it 
is rolled into the cast iron body. 

(79) Drop check valves. In Fig. 176 is shown the 
common type of drop check valve with the construction 
and names of the various parts. As steam or water enters 
from the left it raises the disc and passes out to the right. 
As soon as the pressure is relieved from the left the disc 
drops back in place, preventing any return passage. 
Fig. 177 is of the vertical drop check valve to be used 
on any vertical section of pipe. The objection to the 
valve shown in Fig. 176 is the same as that against globe 
valves , Fig. 166, i. e., it diminishes the pressure. 

Swing check valves. To eliminate the objection to the 
drop check valve the swing check has been designed as 
shown in Figs. 178 and 179. Type (a) is perhaps prefer- 


ASSEMBLY DRAWING. 


143 



Fig. 180 



























144 


MECHANICAL, DRAFTING. 


able, as it presents a more perfect passage for the water 
than type (b). 

(80) Water pipe and boiler tubes. In speaking of a 
2" water pipe it should be understood that the inside 
diameter of the pipe is indicated, the inside diameter 
being necessary to compute the quantity of fluid passing 
thru the pipe. On the other hand a 2" boiler tube is a 
tube whose outside diameter is 2", the outside diameter 
in this case being necessary to compute the heating sur¬ 
face and horse power of a boiler. 

PIPE CONNECTIONS 

(81) Pipe coupler. In Fig. 180 is shown a pipe con¬ 
nection known as a coupler, used in connecting lengths of 
pipe into a line. 

Ground joint union. In Fig. 181 is shown a pipe con¬ 
nection known as a union, to be used in a pipe line where- 
ever it is likely that the pipe may have to be uncoupled 
for repairs, etc. 

Flange union. In Fig. 182 is shown a connection 
known as a flange union which is used as a substitute for 
the union mentioned above on most all pipes of diameter 
greater than 2 y 2 ". 

t 


ISOMETRIC PROJECTION. 


145 


LESSON 9 

ISOMETRIC PROJECTION 

(82) Definition and explanation of principles. Tho 

the fundamental principles depend upon orthographic 
projection, they are so easily understood that it will be 
possible for the student to grasp them fully even with a 
limited knowledge of orthographic projection. Isometric 
projection, as the term indicates, is a projection of equal 
or proportional measurements. If thru a given point 
called an origin, three lines be drawn at right angles to 
each other, e. g., the three adjacent edges of a cube, we 
have the three coordinate axes, x, y, and z known in ana¬ 
lytic geometry. A fourth line passed thru the given point 
and at equal angles with the first three lines is known as 
the Isometric Axis; it may be compared to the diagonal 
of a cube. 

A plane perpendicular to this axis is the isometric pro¬ 
jection plane; for, since the coordinate axes make equal 
angles with the isometric axis they must make equal 
angles with this projection plane; and equal lengths on 
the coordinate axes or on lines parallel to the axes will 
project as lines of equal length on this plane. 

DIRECTRICES 

(83) The orthographic projections on this plane of 
the coordinate axes are known on the drawing as the 
directrices, and occasionally as the isometric axes. Since 
the coordinate axes make with each other equal angles, 
their projections (the directrices) also make equal angles 
(120 degrees) with each other. This being true, when it 


146 


MECHANICAL DRAFTING. 




Fig. 184 



B 



•120 


















ISOMETRIC PROJECTION. 


147 


is desired to make any isometric projection the directrices 
may be drawn immediately thru a chosen point and at 
120 degrees to each other. One of the directrices is usu¬ 
ally taken vertical, Fig. 183; however, the arrangements 
shown in Fig. 184 and 185 are frequently used. 

ISOMETRIC SCALE 

(84) Since the coordinate axes are oblique to the iso¬ 
metric plane their projections are shorter than the axes 
themselves. Each coordinate axis makes with this iso¬ 
metric plane an angle of about 35 degrees. Then assum¬ 
ing the hypotenuse, AB, of the right triangle, Fig. 186, 
to be one of the coordinate axes, BC, the isometric axis , 
and CA, the isometric plane, viewed edgewise, the iso¬ 
metric projection of any given length, DE, on the axis 
BA, would project on the plane with length equal to de. 

To make the isometric projection of proper propor¬ 
tions, divide the hypotenuse of a triangle similar to ABC 
into inches, etc., and project these inches upon CA. 
This scale obtained on CA is known as the isometric scale 
and lines parallel to the directrices should be measured 
according to it instead of to the architect’s scale. 

Problem 1. To construct the isometric projection of 
any parallelopiped. 

Construction. Cube 2" on edge, Fig. 187. 

Thru point 0 are drawn the axes OB, OA, and OC, 
making with each other angles of 120 degrees. From 0, 
along OA, measure with the isometric scale 2"; the same 
along OC and OB to points D, E, and F. OD and OE 
then represent the two adjacent sides of the base, and 
lines from D and E parallel to OE and OD complete the 
base. In similar manner the vertical faces DOF and FOE 


148 


mechanical, DRAFTING. 






















ISOMETRIC PROJECTION. 


149 


are completed; then draw the top base FS and finally the 
faces SD and SE. 


IRREGULAR OBJECTS 

(85) Inasmuch as all but a very small percentage of 
machine parts are either of rectangular shape or can 
easily he enclosed in such a box or parallelopiped, the iso¬ 
metric projections of irregular objects are easily con¬ 
structed with the aid of such an enclosing parallelopiped, 
Fig. 188. 

CIRCLES 

(86) Problem 2. To construct the isometric projec¬ 
tion of a circle. 

8 POINT METHOD 

Construction. ABCD is the isometric projection of 
a square in which a circle is inscribed. On edge AB con¬ 
struct a square and inscribe in it a circle. Draw the hori¬ 
zontal diameter of this circle and diagonals of the square. 
The points of tangency of the circle with the square and 
the 4 points of intersection with the diagonals constitute 
the desired 8 points. If the diagonals of the parallel¬ 
ogram be drawn the isometric projections of these 8 
points may be obtained as shown and the ellipse drawn 
thru them freehand. Fig. 189. 

APPROXIMATE MECHANICAL METHOD 

Fig. 190 illustrates an approximate mechanical method 
for obtaining the isometric projection of a circle. 


150 


MECHANICAL DRAETING. 
















ISOMETRIC PROJECTION. 


151 















152 


MECHANICAL DRAFTING. 


















isometric projection. 


153 


DIMENSIONING 

(87) In placing dimensions on an isometric drawing, 
tlie same rule must be followed as in orthographic work¬ 
ing drawings; the dimensions must read from left to right 
or from the bottom up. In following this rule it will be 
found always that the dimension lines are parallel to the 
coordinants axis, never otherwise. In giving the diam¬ 
eters of circles the method shown in Fig. 191 is preferable 
to placing the diameter directly on the isometric of the 
circle. On inspection of Fig. 192 it is seen that there are 
actually three faces of the object to be dimensioned and 
in giving the dimensions for face No. 1, which is parallel 
to the isometric plane No. 1, it must first be decided what 
directions constitute from left to right and from bottom 
up. The same thing must be decided for faces 2 and 3. 
In Fig. 195 is given a key which will be useful in dimen¬ 
sioning. In connection with this key it will be necessary 
for the student, in placing dimensions, to decide merely 
to which face of this key his dimensions are parallel, 
Figs. 193, 194. 

SHADES AND SHADOWS IN ISOMETRIC OELIQTJE 
PROJECTION 

(88) Shades and shadows, in isometric projection as 
in orthographic projection, are used merely for the 
natural appearance which they give to a drawing. Hence, 
as in orthographic projection, the draftsman has con¬ 
siderable freedom in determining both the direction and 
the length of the shadows. Before proceeding with a 
problem in shades and shadows it will perhaps be well 
to define a few of the terms and state the fundamental 
principles which govern construction. 


154 


MECHANICAL, DRAFTING 


N F 



Fig. 196 










































ISOMETRIC PROJECTION. 


155 


Direct light. All light which comes to any body di¬ 
rectly from the source, the snn, arc lights, etc., is known 
as direct light. 

Indirect light. All light which reaches objects in an 
indirect way, e. g., by reflection from other objects which 
are in direct light, is known as indirect light. 

Shade. Any portion of the surface of an object from 
which the direct light is excluded by some part of the 
same object is said to be in shade. This shaded surface 
may also be known as a shade. 

Shadow. Any portion of the surface of an object from 
which the direct light is excluded by some part of another 
object is said to be in shadow, and for convenience may 
be called a shadow. 


PRINCIPLES 

1. All rays of light in these problems are regarded as 
parallel; hence, when the direction of the first ray has 
been assumed, all others must be considered parallel to it. 

2. The shade or shadow of a given point on a given 
surface is the point in which a ray thru the given point 
pierces the given surface. 

3. Any ray used to determine the shade or shadoiv of 
a given point may in reality be a ray of light; however, 
in this discussion it will be known as a shadow ray; see 
Miller’s Descriptive Geometry, Art. 124. 

4. If a line AB is parallel to a plane, e. g., H, the 
shadow of AB on H is parallel and equal in length to AB. 

5. If lines AB and CD are parallel the shadows of 
AB and CD on any plane must be parallel, i. e., the 
shadows of parallel lines are parallel. 


156 


MECHANICAL DRAFTING. 



Fig. 196 
































isometric projection. 


157 


6. If a line AB is oblique to H, AB and its shadow 
on H will meet at the point in which AB pierces H. 

7. The shadows of parallel lines on parallel planes 
are parallel. 

Problem. To find the isometric or oblique of the 
shade and shadow on H of a given object. 

Given. Isometric and oblique projections of Cross, 
Fig. 196. 

Req’d. Isometric and oblique projections of shade and 
shadow on H. 

Beginning with point 0 as an origin, a line may be 
drawn in any desired direction, e. g., 0 a, to represent the 
shadow of OA, and point a assumed in any desired posi¬ 
tion as the shadow of point A. A a is the isometric pro¬ 
jection of the shadow ray thru A, and all other shadow 
rays must be parallel to A a. Since AB is parallel to H, 
its shadow ab is parallel and equal in length to AB. BC 
is parallel to OA, hence its shadow be is parallel to 0 a, 
and c is determined by shadow ray C c. CD is parallel to 
H, hence its shadow cd is parallel and equal in length to 
CD; d may likewise be located by the shadow ray D d. 
Since the plane GCDK is parallel to H, the shade of GE 
on this plane is parallel to 0 a, see Principle 7, and e is 
located by the shadow ray from E. EF is parallel to 
GCDK, hence the shade line from e is parallel to EF; 
if the arm of the cross were not in the way, the shadow 
of E would fall at e 1 ; EF is parallel to H, hence ej is 
parallel and equal in length to EF; fn is parallel and 
equal in length to FN. It is readily seen from the direc¬ 
tion of 0 a that the face AOM must be in shade, likewise 
BCD and GEFK and space KGe-. 


158 


MECHANICAL DRAFTINC 





Fig. )98 


Fig. 198 


Fig. 199 


Fig. 197 


Fig. 199 


















ISOMETRIC PROJECTION. 


159 


The isometric projections of the shadows of the re¬ 
maining points are located successively as those already 
found. 

LIFTING JACKS 

(89) Lever jack. In Fig. 197 is shown the lever type 
of jack used in lifting moderate loads rapidly. The 
speed with which this jack can be used is the main point 
in its favor. 

Screw jacks. In lifting excessive loads the common 
jack used is the screw. The screw is turned by a bar 
inserted in the hole of the capstan head, running the 
screw either up or down. Fig. 198. 

Hydraulic jack. Where extreme loads are to be lifted 
the hydraulic jack, Fig. 199, will be found most useful. 
The jack is composed of two cylinders and two pistons, 
the larger piston being forced up by the pressure of the 
fluid pumped into the cylinder by the smaller piston. 
Alcohol or oil may he substituted for water if the jack 
is to be used in cold climates. 

CONSTRUCTION OF GEARS 

(90) Cog wheels, pinions, etc., are first cast blank, as 
shown in Fig. 194, and the solid rim later cut into cogs 
on a milling machine. 


160 


MECHANICAL, DRAFTING. 




M 

Fig. 210 



























































OBUQUK projection. 


161 


LESSON 10 

OBLIQUE PROJECTION 

(91) Inasmuch as circles are so rarely found in such 
positions that their projections are true circles in iso¬ 
metric projection, a variety of projection has been de¬ 
vised in which it is possible so to place circles that their 
projections are circles and are easily drawn. This is 
known as oblique projection. 

Inasmuch as the principles of oblique projection 
depend upon the theory of perspective, it will perhaps 
be better not to attempt any explanation of principles. 
Likewise, it may be well to mention that oblique projec¬ 
tion is almost entirely a combination of incorrect prin¬ 
ciples, tolerated merely because of the ease with which 
this projection can be handled. The directions of the 
three directrices or oblique axes are correct; it is true, 
also, that when placed in one of the coordinate planes 
the oblique projection of a circle is a circle; with these 
exceptions the theories are incorrect. The principles on 
which oblique projections are made are as follows: 

AXES AND CO-ORDIDNATE PLANES 

(92) Thru the origin, 0, Fig. 200, a and b, are drawn 
three directrices or axes as shown; one horizontal, a 
second vertical, and the third to the right or left at 45°, 
30°, or 60° with the horizontal, preferably 45 degrees. 
These three lines represent lines at right angles to. each 
other, and may be compared to the three adjacent edges: 
of a cube. 


162 


MECHANICAL, DRAFTING. 










OBIJQUE PROJECTION. 


163 


Taken two and two, these axes include coordinate 
planes as follows: OA and OB, plane 1, or the plane of 
true circles; OB and OC, plane 2, a second vertical plane, 
and OA and OC, plane 3, a horizontal plane. 

DIMENSIONING 

(93) In oblique as well as in isometric projection,* 
the problems of dimensioning are threefold; i. e., any 
object drawn may have faces parallel to each of the three 
coordinate planes in Fig. 201. In placing dimensions 
for constructions on these faces it is necessary, of course, 
to decide what directions constitute from left to right 
and from bottom up. The key in Fig. 202 may be used 
in a manner similar to that of the key given for isomet¬ 
ric projection. Inspection of Figs. 203-207 may serve to 
clear up any doubtful points, both in dimensioning and 
in construction. 

OBLIQUE SCALE 

(94) If equal distances be measured from 0 along 
the axes OA, OB and OC, Fig. 208, the distance along 
OC will appear to be longer than those along OA and 
OB; hence, for symmetry, it is necessary to make use of 
the oblique scale in measuring any distance along OC. 
The oblique scale is obtained by measuring off inches, 
etc., on the hypotenuse of a 45°, 30°, or 60° triangle and 
projecting these inches upon either of the legs for 45°, 
long leg for 30° and short leg for 60° (Fig. 209). 

Problem 4. To draw the oblique projection of a 
parallelopiped. 

Construction. Cube 1" on edge. 

Thru a chosen point, O, Fig. 210, draw the three axes 


164 


MECHANICAL DRAFTING. 




















OBLIQUE) PROJECTION. 


165 






























166 


mechanical drafting. 



Fig. 206 



































OBLIQUE) PROJECTION. 


167 





























168 


MECHANICAL, DRAFTING. 




























OBLIQUE) PROJECTION. 


169 


OA, OB, and OC. Along axes OA and OB measure 1" 
to D and S, and with the oblique scale measure 1" along 
OC to R. Complete the parallelograms ODMR, OSLR, 
and DNSO; then the remaining faces may easily be 
added. 


CIRCLES 

(95) Point E, in face TLRM, is the center of a circle 
%" diameter. Since this is the face of true circles , the 
circle may be constructed with the compass. If it is 
desired to draw the projections of circles lying in faces 
TNSL or NTMD the 8-point method explained in iso¬ 
metric projection may be used. 

If the oblique axis be drawn at an angle of 30 degrees 
to the horizontal it will be noted, in Fig. 211, that face 
NM is now of such shape as to convert the oblique pro¬ 
jection of any circle placed in that face into an isometric 
projection , and the mechanical method of constructing 
that isometric projection, shown in Pig. 190, can and 
should be used. If, on the other hand, the oblique axis 
be drawn at an angle of 60 degrees to the horizontal, 
Fig. 212, the face NL is now of such shape as to convert 
the oblique projection of any circle placed in it into an 
isometric projection which can be constructed mechan¬ 
ically by the method of Fig. 190. 

With some care it will now usually be possible, in 
making the oblique projection of any object containing 
circles, so to place the object that the oblique projections 
of some of the circles are true circles , while the projec¬ 
tions of the remainder become isometric when the ob¬ 
lique axis is drawn either at 30 or 60 degrees to the 
horizontal. 


170 


MECHANICAL DRAETING. 




































































oblique: projection. 


171 


IRREGULAR OBJECTS 

(96) All that has been said on these subjects under 
isometric projection applies as well in oblique projection. 
It is perhaps unnecessary to suggest that when making 
any oblique projection care should be taken so to place 
the object that most of the circles will appear as true 
circles. 

CONVERSION OF IRON ORES INTO COMMERCIAL 
IRON AND STEEL 

(97) Ores. The ores from which pig iron is made 
are three in number: 1. Iron carbonate, a compound of 
iron and carbon, also known as specular iron, from 
which about 1% of the commercial iron in use is made. 
2. Magnetite, a compound of iron and oxygen, known as 
magnetite because of its slight magnetic properties, from 
which about 13% of the iron in use is made. 3. Hematite, 
also an oxide of iron, and of two varieties, red and 
brown, from which the remaining 86% of commercial 
iron is made. Hematite is a heavy reddish brown ore 
which is found in various localities over the country, two 
very important deposits being the Lake Superior, of 
Michigan and Wisconsin, and the Alabama, about Bir¬ 
mingham. In some localities the ore is found near the 
surface, and is so weathered or rotted that it can be 
scooped out by steam shovels; this is the case in the Lake 
Superior regions. In other localities the ore is so hard 
and in such masses that it is necessary to blast it out. 

Conversion of iron ore into pig iron. The iron ore 
as taken from the mines is hauled to the furnaces and 
crushed to egg or walnut size. In converting the iron 
ore into pig iron it is necessary to take from the ore the 


172 


MECHANICAL DRAFTING. 























































































OBUQUE PROJECTION. 


173 


oxygen and combine with the iron in place of the oxygen 
a small percentage of carbon. To accomplish this, coke 
and crushed limestone are mixed with the ore and fed 
into the furnace, a section of which is shown in Fig. 213. 

The coke is principally carbon, and the limestone a 
compound of calcium or lime and silica or plass. As the 
charges of ore, coke, and limestone are fed into the top 
of the furnace, the large bell valve at the top opens from 
the weight, closing immediately after the charge is in, 
thereby preventing the escape of gases thru the top of 
the furnace. This charging o.f the furnace is carried 
on at regular intervals both day and night. It takes 
about 36 hours for the ore to drop from the top of the 
furnace to the bottom and be drawn off as pig iron. As 
it gradually drops, the heat generated by the burning 
of part of the coke by the heavy blasts of air forced in 
at points indicated, heats it to the melting point, where 
carbon from the coke combines with the oxygen of the 
ore, making two gases, carbon monoxide and carbon 
dioxide, which work their way to the top of the furnace 
and are drawn off thru a pipe at the side. As the carbon 
takes the oxygen from the ore, a small percentage of 
carbon combines with the iron in the place of the oxygen, 
and the dirt of the ore, clay, etc., combines with the 
melted limestone to form what is commonly known as 
slag. The pure iron drops to the bottom of the furnace, 
to the hearth, and the melted slag floats on this melted 
iron. At regular intervals the slag is drawn off in cars 
and hauled to dumps, and the iron drawn off and molded 
into pigs. Two methods are used in the molding of this 
iron, the one by converting a considerable space of 
ground, covered with sand, in front of the furnace, into 
one large mold. A large trough leads from the furnace 


174 


MECHANICAL DRAFTING. 











































oblique; projection. 


175 


down thru the center of the yard; smaller lateral troughs 
lead from this large trough, and individual troughs feed 
into the depressions where the pigs are to be cast, Fig. 
214. The second method is by a molding machine con¬ 
sisting of two endless chains carrying between them 
soft steel molds, into which the pig iron is poured at the 
furnace. These chains, moving slowly, pass the molds 
of iron thru a tank of water, cooling them, and on to a 
point where they are automatically unloaded and the pigs 
of iron dropped into cars, Fig. 215. 

Pig iron is rather soft, and when melted in cupolas 
of a foundry, to be run into castings, it is usually neces¬ 
sary to add a certain quantity of scrap cast iron to make 
the metal harder. 

Bessemer steel. To convert pig iron into one of the 
classes of steel used in making railroad rails and stand¬ 
ard construction iron, the melted iron is hauled in cars 
from the blast furnace to what is known as the Bessemer 
converter, Fig. 216. This converter is supported on two 
pinions or trunions, and can be tipped over to pour the 
charge in or out. After the charge of melted iron is 
poured into the converter and the converter shifted up¬ 
right, air at about twenty pounds pressure and heated 
to about 800° F. is forced into the converter as indicated, 
causing the iron to boil most violently. This air both 
burns out some of the carbon and blows out any slag 
which may be left in the iron. This boiling is continued 
from ten to twenty minutes and discontinued when the 
flame from the mouth of the converter takes on a cer¬ 
tain color. The converter is then tipped over and a quan¬ 
tity of the compound of iron and nickel, known as 
Spiegeleisen, thrown in. After boiling for a minute or 
two more, to mix this nickel thoroly thru the mass, the 


176 


MECHANICAL, DRAFTING. 


iron is cast into large billets, which are later rolled into 
steel rails, etc. This steel coming from the converter is 
known as Bessemer Nickel Steel, Bessemer Manganese 
Steel, etc., according to the alloy which was added to give 
it greater strength. 

Wrought iron. To make wrought iron, pig iron is 
broken into pieces and placed on the slag-covered hearth 
of what is known as the reverberating furnace, Fig. 217, 
so called from the fact that the top is so shaped as to 
throw the gas flame directly down on the mass of-iron. 
As the pig iron becomes plastic it is stirred by rods, 
worked thru holes in doors about the furnace, until most 
of the slag that remains in the iron when poured from 
the blast furnace has been worked out; it is then allowed 
to cool slightly and taken out and rolled into a sheet. 
After several of these sheets have been rolled they are 
heated and welded together and rolled into the wrought 
iron bars of commerce. The process of working the slag 
out of the iron in the reverberating furnace is called 
puddling. 

Crucible or tool steel. Crucible steel, which is used 
for all varieties of cutting tools, is made from wrought 
iron. Bars of wrought iron are cut into pieces and 
about 100 lbs. of these pieces, with perhaps 1 lb. of char¬ 
coal, is placed in a covered earthen crucible and heated 
in a furnace until the iron has been melted and has ab¬ 
sorbed all of the carbon. This iron is then cast into 
small billets and later rolled into convenient bars for 
tools. The introduction of the carbon into the wrought 
iron has given to the resulting compound the property of 
extreme hardness. 


OBRIQUE PROJECTION. 


177 


Open hearth steel. A second class of steel, known as 
open hearth steel, is made in a furnace similar to the 
reverberating furnace used in manufacturing wrought 
iron. This steel is made, however, by working into the 
melted pig iron a quantity of scrap iron, producing in 
general a steel of a better quality than the Bessemer. 
This class of steel can be used for steel rails, I beams, and 
in sheets for the making of boilers, etc. The Bessemer 
steel mentioned above is ordinarily used only for rails 
and construction iron, and not for boiler iron. 


178 


MECHANICAL DRAFTING. 


LESSON 11 

MACHINE SKETCHING 

(98) Definition. A machine sketch may be roughly 

defined as a f reehand working drawing. 

To the engineer no one accomplishment is of more 
value than the ability to make rapidly accurate, legible 
machine sketches. 

A draftsman or shop foreman may be called upon at 
any time to make a hasty sketch of some broken machine 
part which perhaps cannot be removed without shutting 
down the machine for a day or two. 

A construction engineer putting in some new machin¬ 
ery may find that some plates, fixtures, etc., designed 
especially for the job, are all wrong, and he must imme¬ 
diately send in sketches of what is wanted. 

A bridge engineer may find his work held up by the 
breaking or absence of some peculiarly shaped piece, or 
may need some special fixtures to handle difficulties pecu¬ 
liar to the job. 

Likewise, it is understood that all machine forms are 
devised in the mechanic’s brain and must be placed on 
paper in some approximate form before it is possible to 
make a mechanical working drawing. 

In all of these and hundreds of other cases which are 
inevitable, the ability to sketch rapidly and well is indis¬ 
pensable, and the man who finds himself called upon to 
make a sketch and is not well grounded in its principles, 
will find himself seriously handicapped. 

(99) Paper. It will be seen that the nature of the 
.situations which require sketching will demand the use 


MACHINE} SKETCHING. 


179 


of scratch paper or a notebook. Cross-section paper is 
invaluable for this purpose, as it aids materially in the 
rapid and accurate sketching of the several views. 

(100) Nature of drawing. As in a mechanical work¬ 
ing drawing, a machine sketch consists of a number of 
views (top and front; top, front, and left end, etc.) of a 
machine or machine part. These views are true ortho¬ 
graphic projections, hence projections of each other, as 
in working drawings. Never show more views than are 
necessary to explain clearly the construction; of course, 
two are a minimum; variations in this respect will be 
mentioned later. 

(101) Pencil—Sketch stroke. For sketching it will 
be better to use a comparatively soft pencil, H or 2H, 
as it is desirable to show marked distinction between the 
outlines of the object and dimension and section lines. 

In drawing lines, whether short or long, the sketch 
stroke should be used. The sketch stroke is merely a 
succession of short strokes in the desired direction, and, 
as a result, the line will, of course, be somewhat ragged, 
consisting of a number of short overlapping lines. How¬ 
ever, by this method it will be found possible to approxi¬ 
mate a straight line much more closely than by a con¬ 
tinuous stroke. 

(102) Size of drawing. The work being freehand 
and done usually under adverse conditions, sketches are 
not made to scale; numerical dimensions are depended 
upon entirely for sizes. As an aid in approximating 
proportions of the different parts of a machine, the fol¬ 
lowing scheme will be found useful: Suppose after care¬ 
ful inspection it is decided that only two views are 
necessary, and these front and right end. You have 
perhaps a 5 x 7 notebook at hand and must place these 


180 


MECHANICAL, DRAFTING. 


two views, with dimensions, on this size sheet. Estimate 
the ratio of the length of the object to its width and 
height and block out roughly on the sheet the proper pro¬ 
portional spaces, for the two views, making them as large 
as possible. Then measure off on a lead pencil with the 
thumb-nail a distance equal to the length you have given 
the space for the front view, and, holding the pencil hori¬ 
zontally and about V from the eye, move off from the 
machine until the space from the end of the pencil to the 
thumb-nail just covers the length of the machine. Stand¬ 
ing in this position and using the pencil in this manner, 
the several parts of the machine may be rapidly sketched 
in in their proper sizes. 

(103) Procedure. In making a machine sketch, the 
greatest speed and accuracy will be attained by follow¬ 
ing some system. The following will be found valuable: 

1. Decide on the number of views necessary, and 
decide which these should be. 

2. Estimate ratio of length to width of machine and 
block out on sheet proportional spaces for above views. 

3. Sketch in all outlines (working on all views at 
the same time). Do not attempt to finish one view en¬ 
tirely before working on the other; when a line is placed 
on one view, place its projection on the other view so 
that all views are finished at approximately the same 
time. 

4. Sketch in dimensions, auxiliary, and section lines. 
The reason for placing on dimension lines while making 
up the views is, that each detail of the piece as it is 
drawn may suggest a necessary dimension that perhaps 
would be overlooked if left until later. A break should 
be left in each dimension line. No attempt need be made 
here to distinguish between outline and other lines. 


MACHINE SKETCHING. 


181 


5. Go over the sketch carefully and increase the 
weight of outlines so that the construction shows easily. 

6. Obtain from the machine with calipers and rule 
all dimensions already indicated on sketch. Always 
place on overall dimensions as a check. 

7. Be liberal with notes. 

(104) Short cuts. To save time, the following short 
cuts are permissible: 

1. In drawing objects of familiar shape, wheels, etc., 
the hub, two spokes, and a short portion of the rim is 
sufficient. 

2. Where objects are symmetrical with respect to a 
center line, e. g., gate valves, etc., it is sufficient to show 
only one-half of object, limiting the portion drawn by 
the center line. The other half may be drawn in when 
time permits, if desired. 

3. Where objects are symmetrical about two center 
lines at right angles to each other, it will be sufficient to 
show only one-fourth of the object. 

4. Where any part cannot be shown well in detail, 
e. g., bolts, holes, fasteners, etc., explanatory notes may be 
substituted—e. g., %" drill; % x 10 pi. tap; %" Hex. 
Hd. Mach. Sc.; etc. 


182 


MECHANICAL DRAFTING. 


LESSON 12 

PERSPECTIVE 

(105) Perspective. Tho it is impossible to give here 
any complete explanation of the principles of perspec¬ 
tive, it has been deemed advisable to attempt sufficient 
explanation to enable engineers, who have no other such 
opportunity while in college, to understand a few of the 
basic principles. 

It is readily seen that no one view of a working draw¬ 
ing of any object can present to the eye the natural 
appearance possessed by a crayon or charcoal drawing. 
The reason is, that in making a working drawing the 
eye was imagined at an infinite distance from the object, 
an assumption so unnatural as to give rise immediately to 
results of an unnatural appearance. 

(106) Perspective drawing defined. A perspective 
drawing of an object is such a representation of that ob¬ 
ject on a given plane or sheet of paper as will present 
the same appearance as the object itself when the eye is 
in a certain position with respect to the object. 

The plane on which the perspective drawing is made 
is called the picture plane, and, for reasons which need 
not be given here, is usually taken vertically. 

(107) Principles of construction. The principle on 
which perspective construction is based is as follows: 
The vertical picture plane is placed between the eye and 
the object (that the drawing may be smaller than the 
object), and lines of sight or visual rays drawn from the 
eye to the various points of the object. The points in 
which these lines pierce the picture plane are respectively 


PERSPECTIVE. 


183 


the perspectives of the corresponding points of the ob¬ 
ject. If lines he drawn connecting these piercing points 
in their proper order, a perspective drawing of the whole 
object is obtained. 

(108) Picture plane and position of object. Since 
perspective drawings are made mostly from working 
drawings, the vertical plane of orthographic projection 
is used as the picture plane and the object placed in the 
third angle. 

(109) Position of point of sight. The point of sight 
is, of course, in front of the vertical plane, and may be 
in either the first or fourth angles, according to the nature 
of the view desired; i. e., if it is desired to make a draw¬ 
ing showing the appearance of the object when directly 
in front of it, the point of sight would be in the fourth 
angle. 

(110) Principal point in perspective. The projection 
of the point of sight on the vertical plane is called the 
principal point in perspective, and is of prime impor¬ 
tance in construction. Inasmuch as the vertical projec¬ 
tions of points are designated thus, a', b', c', etc., the 
vertical projection of the point of sight, S, will be indi¬ 
cated by s'. 

(111) Principal point the vanishing point of lines 
perpendicular to the picture plane. It is a familiar fact 
that as one stands near a long straight section of rail¬ 
road track the two lines of rails appear to meet off in the 
distance. So it is with any set of parallel lines; if the 
eye follows them for a distance—and, when speaking geo¬ 
metrically, we give this distance a value of infinity — 
they all appear to meet in one point. This point we call 


184 


mechanical, drafting 




Fig. 218 


















































perspective;. 


185 


their vanishing point. When our line of sight follows out 
these parallel lines to infinity, where they appear to meet, 
for all practical purposes the line of sight is parallel to 
the given set of lines. Reference to Fig. 218 may serve 
to make this explanation clearer. Point S represents 
the position of the eye. A cube AB rests on a horizontal 
plane on the other side of the picture plane. The four 
parallel edges, AB, CE, etc., of the cube are produced as 
indicated by dotted lines to the right; if they are pro¬ 
duced an infinite distance they will appear to meet, and 
the line of sight from S to the apparent meeting or 
vanishing point is the line thru S and Y. Then, as ex¬ 
plained above, if SY meets AB, CE, etc., at infinity, it 
is parallel to them. But AB, CE, etc., are perpendicular 
to the picture plane; therefore the line thru S and Y out 
to this vanishing point is also perpendicular to the pic¬ 
ture plane and must pass thru s', the projection of S on 
the picture plane. As viewed from point S, the four 
edges, AB, CE, etc., which we have produced to infinity, 
do not in reality appear to be parallel lines forming the 
edges of a long prism, but seem to represent the four 
edges of a long pyramid. To return to the perspective, 
suppose we wish to represent this long pyramid on the 
picture plane as seen from S. According to Art. 107, 
lines are drawn from S to the several points of the 
pyramid; the line from S to the imaginary apex at in¬ 
finity pierces the picture plane at s ; and the lines from 
S to A, C, D, and F pierce the picture plane at a x c x d x f x ; 
then a x c x d x f x -s' is the perspective of the pyramid. From 
this explanation it is seen that the perspective of all lines 
perpendicular to the picture plane meet at s', the vertical 
projection of the point of sight. For this reason s' is 
called the vanishing point of perpendiculars. The fact 
that perpendiculars do converge at s' affords an easy 


186 


MECHANICAL, DRAFTING. 


method of constructing the perspective of any object 
when placed in a certain position. Lines from S to the 
other points of the cube are seen to pierce the picture 
plane in points on the perspectives of these perpendicu¬ 
lars, giving the figure b x a x c x d x f x g x . This figure repre¬ 
sents the cube as seen from S. Face ABEC is not visible 
from S. 

(112) The horizon in perspective. Any line which 
is perpendicular to a vertical plane is horizontal. In 
Fig. 218 the lines AB, CE, etc., are horizontal lines and, 
when produced an infinite distance, appear to meet in a 
point on what we commonly call the horizon. Then the 
line of sight from S to this meeting point becomes a 
horizontal line, and the perspective of the horizon will 
be the horizontal line drawn thru the point s'. The 
horizontal line lying in the picture plane and passing 
thru the vertical projections of the point of sight, s', is 
also called the horizon. 

(113) One face of the cube coincides with picture 
plane. If the cube in Fig. 218 be moved until face ACDF 
coincides with the picture plane, then this face becomes 
its own perspective and each line on this face is shown 
in its true value; i. e., a circle shows as a true circle, etc. 
From this it follows that the perspective of any circle 
whose plane is parallel to the picture plane will be a true 
circle; its diameter will be less or greater than the true 
diameter, however. 

(114) Mechanical Construction of a Perspective. 

Inasmuch as all lines in perspective are shorter than the 
lines which they represent, except in the case of lines 
which lie in the picture plane, it will be best to put one 
face of the object or one face of a circumscribed paral- 


PERSPECTIVE. 


187 


lelopiped into coincidence with the picture plane, in 
order that we may have a foundation of actual measure¬ 
ments on which to base our construction. 

(115) Coordinates. The position of the point of sight 
wdth respect to some chosen point, A, of the object will 
hereafter be given as follows: 

x = distance of point of sight to right or left of A 
as x is + or —. 

y = distance of point of sight above or below A as y 
is + or —. 

z — distance of point of sight before the picture 
plane; e. g., x = 3", y = — 4", z = 6" locates S 3" to the 
right and 4" below A and 6" before the picture plane. 

Problem 5. To draw the perspective of a cube 1%" 
on edge, one face of the cube coinciding with the picture 
plane; x— — 2", y = 1", z = 4". A is taken at corner F. 

Construction. See Fig. 219. 

Draw well toward the top of the sheet a horizontal 
line G. L., the intersection of the horizontal and vertical 
planes. Construct in a convenient position the top view 
b-ac-df-gj of the cube; the edge af, which represents the 
top and front edge, coinciding with G. L. 2" to the left 
of point / of the top view draw a perpendicular to G. L, 
and 4 " below G. L., on this perpendicular place the point 
s. The top view, G. L., and s, now represent respectively 
the cube, the picture plane, and point of sight, as they 
appear looking down from above. On the perpendicular 
from S to G. L. assume point s at any convenient dis¬ 
tance e. g., below G. L. Then 1" below s' and 
limited on the right by ss ', construct a left side view of 
the cube and measure from s' to the right along a hori¬ 
zontal line thru s' a distance of 4" for point s'. The left 


188 


MECHANICAL DRAFTING. 



Fig. 219 










































PKRSPKCTIV^. 


189 


side, Ss' and s x represent respectively the cube, picture 
plane, and point of sight as they appear from the left. 
Then from the top and side views construct the front 
view ft at c x d x of the cube and draw lines from ft at c x 
and dt to s'. This figure s'—ft a x c x d t then is the per¬ 
spective of the long pyramid spoken of in Art. 103. Con¬ 
nect 5 with the point g of the top view and from the point 
v in which this line intersects Gr. L. drop a perpendicular 
to Gr. L., until it intersects the two lines f x s' and d x s'; 
g x j i is then the perspective of the edge GrJ of the cube. 
A horizontal line from g x produced until it intersects a x s' 
at b x completes the perspective of the cube. It is easily 
understood that the line sg represents a line of sight 
from s to G and was drawn to ascertain the point V at 
which this line of sight pierces the picture plane, or 
rather to determine the distance vd to the left of the 
edge FD of the cube at which that line of sight pierces 
the picture plane. 

It is desired to place a small pyramid on top of the 
cube, the edges of its base parallel to the edges of the 
cube and its axis passing thru the center of the top 
face. Construct the top and left side views in place and 
proceed with the construction of the base as shown. 
After the perspective of the base is drawn the two diag¬ 
onals may be drawn to determine the position of the axis. 
Connect s x and p; s x p intersects ss' at v' ; a horizontal 
line thru v' intersects the axis of the pyramid at p, and 
the pyramid may be completed. The left side view and 
s, enable us to determine the distance above any line of 
the face FACD at which lines of sight pierce the picture 
plane, v' a being the distance above FA at which Sp 
pierces this plane. 


190 


MECHANICAL DRAFTING. 



















































perspective;. 


191 


(116) Circles in perspective. The 8 point method 

may be used in constructing circles in perspective. This 
is illustrated on the cube in Fig. 219. The diagonals can 
easily be drawn and the points of tangency of the per¬ 
spective with the upper and lower lines f x g x and d x j x 
determined by drawing a vertical line thru the inter¬ 
section of the diagonals. 

(117) Irregularly shaped objects. Any irregularly 
shaped object may be easily drawn in perspective by 
first enclosing the object in a parallelopiped and refer¬ 
ring the several constructions of object to lines of the 
parallelopiped. 

(118) Position of point of sight. Considerable care 
and judgment must be used in placing the point of sight, 
for it is easily understood that a house viewed from a 
point only two feet in front of it would look absurd; how¬ 
ever, its perspective can be constructed as easily under 
such circumstances as any other. It is well to estimate 
approximately from what particular position we would 
likely view that object to obtain the best view; taking 
into account the size of the object in this estimate. The 
point of sight may then be placed accordingly. For large 
objects a safe rule is to place the point of sight in front 
of the object a distance equal to twice the greatest dimen¬ 
sion. For smaller objects we may increase this to 4 or 5 
times the greatest dimension. 

THE ELLIPSE 

(119) Definition: An ellipse is a curve generated 
by the motion of a point which moves so that the sum 
of its distances from two fixed points is constant. For 
example, in Fig. 220, the sum, x -f- y, of the distances 


192 


MECHANICAL/ DRAFTING. 




Fig. 221 
Fig. 222 


I IP 'b 'q 


















PKRSPSCTIVK. 


193 


from any point 0 on the ellipse to the two fixed points, 
Fj and F 2 is constant and equal to 2 a. 

Besides being considered a mathematical curve gen¬ 
erated according to a certain law, the ellipse may be 
considered the curve which is cut from the surface of a 
right circular cone by a plane which intersects all of the 
elements and is oblique to the axis. Also as the ortho¬ 
graphic projection of a circle which is oblique to the 
plane of projection. 

The long diameter of the ellipse is known as the 
major axis and the short diameter as the minor axis; in 
analytic geometry these axes are given values of 2a and 
2b, Fig. 220. 

Construction. The ellipse figures so prominently in 
drafting that it will be well to give several methods of 
construction, both exact and approximate. 

Exact Method. (1) From the law according to 
which the curve is generated it' has been found possible 
to construct the ellipse accurately as follows. With 
point 0, Fig. 221, as a center and the axes as diameters, 
describe two circles. Then from 0 draw any number of 
radii of the large circle, e. g., OA, OB, OC, OD, etc. 
The vertices a, b, c, d, etc., of the right angles of the 
right triangles, Aaa ly Bbb ly etc., are points of the required 
ellipse and the curve may be traced thru these points 
either freehand or by means of a universal curve. 

Exact method (2) Trammel method. If from any 
point P, Fig. 222, on the edge of a strip of paper or 
ruler the semi minor and semi major axes be measured 
to points b and a, and this strip or ruler placed over the 
axes and moved so that point b is always on the major 
axis and a on the minor axis, the successive positions of 


194 


MECHANICAL DRAFTING. 

















perspective:. 


195 


point P are points of the required ellipse. These posi¬ 
tions of point P may be marked with a pencil or needle 
point and the ellipse traced thru them. 

Approximate method (1)—4 center method. Con¬ 
nect point B, Fig. 223, with point A. Then with 0 as a 
center and OB as a radius describe the arc cutting OA 
at C; lay off from B, on BA, the distance CA, to Cj. 
The perpendicular bisector of CiA locates two of the 
desired centers and the curve may be drawn with the 
compass as shown. 

Approximate method (2)—8 center method. Con¬ 
struction. Connect points A and B and draw the lines 
AE and BE, Fig. 224. Then describe the quadrant EC 
and erect the perpendicular CD. From point 0 in which 
CD intersects AB draw OR. The arc RF locates center 
No. 1. EF produced locates center No. 3 at K. Con¬ 
nect D and K and produce RF to J; with G and H as 
centers and GJ as a radius describe arcs intersecting at 
center No. 2. Centers, 4, 6, and 8 may then be located 
from 2. It will be noted that center No. 2 does not lie 
on the radius GK; however, it is so small a distance 
from GK that no irregularity can be detected in the 
curves at G. 


196 


MKCHANICAIy DRAFTING. 


LESSON 13 

PHOTOGRAPHIC REPRODUCTION 

(120) Blueprinting. Blueprinting is in short a pro¬ 
cess of simple photographic reproduction on sensitized 
paper, of drawings which have been made on some 
translucent material; this material may be tracing cloth, 
tracing paper, or ordinary paper oiled after the drawing 
has been finished. In common practice the process is 
somewhat rough as one would infer from a glance at the 
average print; however, with care it can be carried 
nearly to the same limits of refinement as other photo¬ 
graphic printing. 


BLUEPRINT PAPERS 

(121) Occasions may arise when it is necessary to 
sensitize paper for blueprinting; however, unless abso¬ 
lutely necessary no draftsman should ever bother to coat 
his own paper, for it is a tedious and most unsatisfac¬ 
tory process. The machine coated papers sold by any 
of the instrument companies in 10 or 50 yard rolls of 
any width and of any desired thickness or quality of 
paper is cheap, keeps well for months in a tin tube, 
and always gives better results than paper coated by the 
amateur. For prints which must stand extra hard use, 
either mounted paper (cloth backed paper) or blueprint 
cloth (a smooth hard surfaced sensitized cloth) should be 
used; the latter, however, seldom gives the sharp detail 
obtainable on paper. Below is tabulated information 
that will be of value in ordering papers or cloth. 


photographic reproduction. 


197 


Blue Print Paper and Cloth 


PAPER 

CEOTH 

Weight 

Use 

Weight 

Use 

Extra thin 

For sending thru mail. 
Not satisfactory for 
shop use, too thin. 

Extra thin 

Earge prints which 
are to receive extra 
hard wear. 

Thin 

For large prints that 
would be too bulky on 
heavier paper. 

Medium 

Small maps, moderate 
sized prints that re¬ 
ceive extra wear. 

Medium 

thick 

Best for all ordinary use, shop, construction work, etc. 

Thick 

For durable small prints; maps, land plots, etc. 


Printing Speed in Bright Sunlight 


Regular 

Rapid 

Extra Rapid 

Elec. Rapid 

4 min. 

2 min. 

40 sec. 

25 sec. 


In ordering paper be sure to state the printing speed desired; 
e. g., 1 roll; 50 yds. x 36 in., Extra Thin, Electric Rapid, Blue Print 
Paper. 


TO SENSITIZE PAPER 

(122) Paper. Only “unsized” and well washed 
papers are suitable for blueprinting. The size used on 
many papers to give it a glossy and easy writing surface 
discolors the blueprint solution immediately. Likewise 
paper from which the sulphur, used in its manufacture, 
has not been well washed will discolor. Practically any 
unsized “bond” or “parchment” paper will be found 
satisfactory for printing. 

Solution. The formula in most common use for the 
sensitizing solution is: (1) Bed prussiate of potash, 1 
oz.; water (distilled), 4 oz.; (2) double citrate of iron 
and ammonia, 1 oz.; water (distilled), 4 oz. As long as 































198 


MECHANICAL, DRAFTING. 


these solutions are kept separate sunlight has no effect 
upon them. However, the second solution should be 
kept in a well stoppered bottle of dark colored glass. 

To sensitize the paper, mix equal volumes of the 
above solutions and apply either with a camel’s hair 
brush, brushing first horizontally, then vertically, to 
insure even coating, or float the paper for a few seconds 
in a shallow granite pan partially filled with the solu¬ 
tion, and hang by one corner to dry. This sensitizing 
must' of course be done in a dark room. If the solution 
of citrate of iron is kept too long it may mold and spoil ; 
hence, as the crystals dissolve quite readily it may be 
best to make this solution only when it is to be used and 
then only what is needed. The bottle in which the citrate 
is kept should be glass stoppered to prevent moisture 
from melting down the crystals. The prussiate does not 
dissolve so readily and as it does not spoil it can be kept 
in solution in any quantity. 

VANDYKE SOLAR PAPER 

(123) Vandyke Solar Paper, sometimes called 
u Brown Print” paper, is a brown paper used in making 
negatives for positive printing. A print is made on Van¬ 
dyke paper from a tracing, the inked side of the tracing 
being in this case turned to the paper, so that a reversed 
print is obtained. The lines of the drawing show up 
white on a deep brown background. This paper is then 
rubbed with oil to make it more transparent and positive 
blueprints are made from it, the brown side of the nega¬ 
tive being turned toward the blueprint paper. In this 
final print the lines of the drawing show up blue on a 
white background instead of the reverse in direct print¬ 
ing from the tracing. 


PHOTOGRAPHIC REPRODUCTION. 


199 


WASHING AND FIXING VANDYKES 

(124) Vandyke paper has been sufficiently exposed 
when the surface not covered by the black lines of the 
tracing has turned a light bronze color. After washing 
for a few minutes, face down in the tank, the print should 
be fixed with a solution of 1 oz. of hyposulphite of soda 
to 1 qt. of water. The print may be laid on a board and 
the solution applied with a brush or better still the print 
may be floated face down, in a granite pan partially 
filled with the hypo solution; one brushing or a few sec¬ 
onds floating is sufficient. The print should then be 
washed again face down, to remove the surplus hypo. 

TO TRANSPARENTIZE VANDYKES 

(125) It is possible to obtain positive prints from 
unoiled Vandykes; however, if the negative has been 
rendered more transparent by oiling the printing time 
will be materially reduced. Any clear oil or white 
grease will answer for this purpose, white tube vaseline 
being perhaps the most convenient. The following for¬ 
mula gives a transparentizing oil that works well: 4 oz. 
banana oil, 10c tube white vaseline. (Mix the two by 
heating slightly and keep in a stoppered bottle.) The 
banana oil furnishes a quick “drier” and the vaseline a 
permanent oil. If there is much transparentizing to be 
done it is well to keep a ball of waste, soaked in the 
above solution, in a covered tin can. Never apply more 
grease than will dry in a few minutes and be sure to 
oil the side of the paper which is to be turned toward 
the light. Unless necessary never use paraffin for trans¬ 
parentizing; it renders the paper very brittle and any 
wrinkles in a paraffined negative show plainly on the 
print. 


200 


MECHANICAL DRAFTING. 


POSITIVES ON OLD VANDYKE PAPER 

(126) In making positive prints on old Vandyke 
paper some little care mnst be exercised. When printed 
and washed the nnexposed or white parts turn decidedly 
yellow; this can be prevented if the print is merely 
dipped in the water to wet the surface and start the 
printing out and immediately floated on the fixer; the 
fixer will print out the lines and prevent the background 
from turning yellow. These precautions are not neces¬ 
sary in making negatives on old paper, for tho unexposed 
parts may turn yellow the negative will print well when 
oiled. 


BLUEPRINTING FROM TYPEWRITTEN SHEETS 

(127) To obtain clear sharp prints from typewrit¬ 
ten sheets a moderately thin hard surfaced paper and 
new black typewriter ribbon should be used. If there is 
much work to be done it will be well to obtain an extra 
heavily inked ribbon. In typewriting place under the 
the paper a sheet of black carbon paper with carbon face 
toward the paper; thus an impression is obtained on both 
sides of the paper. Use each sheet of carbon paper only 
once for this purpose. 

In oiling, one may not rub these sheets, as the carbon 
will smear. Instead, lay over the typewritten sheet a 
square of oily cotton flannel, then a sheet of heavy paper 
and roll with a small picture mounting roll. Or better, 
if time permits, lay pieces of oily cotton cloth between 
the sheets and weight down with a heavy book for sev¬ 
eral hours. Arrange sheets and cloth as follows: Paper, 
cloth, two sheets of paper, cloth, two sheets of paper, 
cloth, etc. In printing from these sheets, over expose 
the paper slightly and wash in water to which hydrogen 


PHOTOGRAPHIC REPRODUCTION. 


201 


peroxide has been added in the proportion of % tea¬ 
spoonful to 2 gallons water; the hydrogen peroxide will 
bring out the over exposed parts and deepen the bine. 
The above solution can be used to advantage in washing 
any blueprints; a sharper contrast between the white 
lines and blue background can be obtained. 

PRINTING FROM OLD BLUEPRINTS 

(128) Occasionally reproductions of drawings are 
wanted when the tracings are not available. By use of 
the “Direct Copier’’ of the Frederick Post Co., Chicago, 
an old blueprint may be rendered sufficiently dense to act 
as a good negative. This “Direct Copier” consists of 
two concentrating solutions to be applied to the old blue¬ 
print to deepen the blue; the transparentizing oil must 
then be used to clear up the white lines. If the “Direct 
Copier” is not available and there is not sufficient time 
for a tracing a fairly good positive may be made from a 
blueprint by merely transparentizing it. 

PRINTING FROM HEAVY CARDBOARD 

(129) If it is desired to make a blueprint of a draw¬ 
ing mounted or printed on heavy cardboard or of a 
drawing on mounted paper, the face of the drawing 
should be soaked with alcohol and immediately clamped 
in the printing-frame. The alcohol will not evaporate 
while closed in the frame nor will it dissolve the blue¬ 
print solution if it should soak thru the cardboard. The 
length of time required for printing will have to be 
learned from experiment. 


202 


MECHANICAL DRAFTING. 


PRINTING FROM COORDINATE PAPER 

(130) Coordinate paper printed in red gives bet¬ 
ter blueprints than the paper printed in bine or green. 
Always transparentize the coordinate paper before 
printing; it will save time in printing and give better 
results. 

(131) Positive blueprinting of typewritten sheets. 

Excellent negatives for positive printing of typewritten 
sheets may be made from new black carbon paper as fol¬ 
lows : Remove the ribbon from the typewriter and place 
the carbon paper in the machine, face up, with a sheet of 
thin hard surfaced paper over it. A reversed impres¬ 
sion will of course be obtained on the back of this sheet 
of paper and the better the quality of paper the more 
clear cut will be the letters on the carbon sheet. The 
reason for placing the carbon with face to the ,cover sheet 
is to obtain such an impression as to make it possible to 
place the carbon side of the paper toward the glass of 
the printing frame instead of toward the blueprint paper. 

Handle the carbon paper very carefully; a finger 
mark or smudge may easily ruin the negative. 

The time for printing will have to be determined by 
experiment; it should be somewhat longer than for print¬ 
ing from tracings. 


U.S.'S. Bolts 8 < Screws 


PHOTOGRAPHIC REPRODUCTION. 


203 






Fig. 127 












































































































































































204 


MECHANICAL DRAFTING. 


REFERENCE TABLES 

KEY FOR THE FOLLOWING TABLES OF BOLTS, NUTS, ETC. 


A=Outside Diameter of Threads and Thickness of Nut. 


B=Threads per Inch. 
C=Tapping Drill. 
D=Across Flats. 
E=Across Corners, Hex. 
F=Across Corners, Sq. 
G=Thickness of Collar. 
H=Thickness of Head. 


I=Across Flats. 

J=Thickness Head and 
Nut. 

K=Diameter Collar. 

S=Width of Slot.—Deci¬ 
mals. 

X=Angle of Head. 


Hexagonal-Head Cap-Screw 


a r 

1/4 | 

5/1d| 

3/8 | 7/16| 1/2 | 

9/16| 

5/8 | 

3/4 | 7/8 

B |20 

|18 

116 

14 |12 |12 |11 


10 | 9 

D 1 

7/16| 

1/2 | 

9/16 5/8 | 3/4 | 

13/16| 

7/8 

1 | 1- 1/8 

E 1 

1/2 | 

37/64j 

41/64| 23/321 51 64 j 

15/16| 

33/64 

| 15/32| 1-19/64 




Square-Head Cap-Screw 



A | 

1/4 | 

5 16| 

3/8 | 7/16J 1/2 | 

9/16 | 

5/8 

| 3/4 | 7/8 

B |20 

|18 

116 

|14 112 |12 

|H 


|10 I 9 

D | 

3/8 | 

7/16| 

1/2 | 9/16j 3/8 | 

11/16 | 

3/4 

| 7/8 | 1- 1/8 

F | 

17/32 

39/64 

45/64] 51 64| 7/8 | 

31 32 j 1- 

1/16 | 1-15/64| 1-19 '32 

Iron Set-Screw 

A 

1 1/4 

| 5 16 

| 3/8 | 7/16 | 1/2 | 

9/16 | 

5/8 | 

3/4 | 7/8 

B 

| 20 

1 18 

| 16 | 14 | 12 | 

12 | 11 | 

10 9 





















RKRFR^NCS TABI^S. 


205 


JJ. S. Standard Bolts and Nuts 




1 


Rough 


Finished 

A 

1 B | 

C | 

D | 

E | F | 

H | 

I | 

J 

1/4 

|20 |10 

1/2 1 

37/'64| 7/10| 

1/4 | 

7/16| 

3/16 

5 16118 | 

1/4 | 

19/321 

11/161 10/12| 

19/641 

17/32| 

1/4 

3/8 

|16 | 

19/64| 

11/16| 

51/o4 63/641 

11/32| 

5/8 | 

5/16 

7/16114 | 

23/64 

25/321 

9/10| 1- 7/64j 

25/64| 

23/32| 

3/8 

1/2 

|13 | 

13/32| 

7/8 

1 | 1-15/64| 

7/16| 

13/16] 

7/16 

9/16|12 

15/32| 

31/32| 

1- 1/8 | l-23/64| 

31/64| 

29/321 

1/2 

5/8 

I 11 1 

33/641 

1- 1/16| 

1- 7/32| 1- 1/2 | 

17/32| 

1 | 

9/16 

3/4 

10 | 

5/8 | 

1- 1/4 | 

1- 7/16| 1-49/64 

5/8 | 

1- 3/16 

11/16 

7/8 

1 9 1 

47/64 j 

1- 7/16 

1-21/32| 2- 1/32| 

23/32| 

1- 3/8 | 

13/16 

1 

1 8 1 

27/32| 

1- 5/8 | 

1- 7/8 | 2-19/64| 

13/16| 

1- 9/16| 

15/16 

1-1/8 

1 7 1 

61/64| 

1-13/16| 

2- 3/321 2- 9/16| 

29/321 

1- 3/4 j 

1- 1/16 

1-1/4 

7 1 

1- 5/64j 

2 | 

2- 5/161 2-53/64| 

1 | 

1-15/16| 

1- 3/16 

1-3/8 

1 6 1 

1-11/64 

2- 3/16 

2-17/32 3- 3/32| 

1- 3/321 

2- 1/8 

1- 5/16 

1-1/2 

1 6 | 

1-19/64 

2- 3/8 j 

2- 3/4 | 3-23/64| 

1- 3/16| 

2- 5/16| 

1- 7/16 

1-5/8 

| 5-l/2| 

1-25/64 

2- 9/16| 

2-31/32| 3-5/8 j 

1- 9/321 

2- 1/2 | 

1- 9/16 

1-3/4 

1 5 1 

1- 1/2 j 

2- 3/4 | 

3- 3/16| 3-57/64| 

1- 3/8 | 

2-ll/16| 

1-11/16 

1-7/8 

5 | 

1- 5/8 | 

2-15/161 

3-13/32| 4- 5/32 

1-15/32| 

2- 7/8 | 

1-13/16 

2 

| 4-1/2 

1-23/32 

3- 1/8 | 

3-19./32| 4-27/64| 

1- 9/16| 

3- 1/16 

1-15/16 

2-1/4 

I 4-1/2 

1-31/32| 

3- 1/2 | 

4- 1/32 | 4-61/64| 

1- 3/4 | 

3- 7/16] 

2- 3/16 

2-1/2 

1 4 1 

2- 3/16 

3- 7/ 8 | 

4-15/32| 5-31/64| 

1-15/16| 

3-13/16| 

2- 7/16 

2-3 4 

1 4 1 

2- 7/16 1 

4- 1/4 | 

4-29/32 6 | 

2- 1/8 | 

4 - 3/16| 

2-11/16 

3 

| 3-l/2| 

2-41/64 

4- 5/8 | 

5-ll/32| 6-l7/32| 

2- 5/16| 

4- 9/16] 

2-15/16 

3-1/4 

3-1/2 

2-57/64| 

5 1 

5-25/32| 7- 1/16| 

2- 1/2 | 

4-15/16] 

3- 3/16 

3-1/2 

3-1 4 1 

3- 1/8 | 

5- 3/8 | 

6-13/64| 7-39/64| 

2-ll/16| 

5- 5/16| 

3- 7/16 

3-3/4 

1 3 | 

3-21/64| 

5- 3 4 | 

6- 5/8 j 8- 1/8 | 

2- 7/8 | 

5-ll/16| 

3-11/16 

4 

1' 3 1 

3-37/64| 

6- 1/8 j 

7- 1/16 8-41/64| 

3- 1/16 

6- 1/161 

3-15/16 

4-14 

| 2-7/8 

3-13/161 

6- 1/2 j 

7- 1/2 | 9- 3/16 

3- 1/4 j 

6- 7/16] 

4- 3/16 

4-1/2 

| 2-3/4 

4- 3/64 

6- 7/8 | 

7-15/16| 9- 3/4 | 

3- 7/16 

6-13/16 

4- 7/16 

4-3/4 

| 2-5/8| 

4- 9/321 

7- 1/4 

8- 3/8 10- 1/4 | 

3- 5/8 | 

7- 3/16 

4-11/16 

5 

| 2-l/2| 

4- 1/2 | 

7- 5/8 | 

8-13/16| 10-49/64 

3-13/16| 

7- 9/16 

4-15/16 

5-1/4 

| 2-l/2| 

4- 3/4 | 

8 

9-15/64 11- 5/16| 

4 I 

7-l5/16| 

5- 3/16 

5-1/2 

| 2-3/8| 

4-63/64| 

8- 3/8 | 

9-ll/16| 11-27/321 

4- 3/16 j 

8- 5/16| 

5- 7/16 

5-3/4 

| 2-3/8| 

5-15/64 

8- 3/4 |10- 3/32112- 3/8 | 

4- 3/8 | 

8-ll/16| 

5-11/16 

6 

| 2-l/4| 

2-29/64| 

9- 1/8 110-17/32| 12-15/16| 

4- 9/16 j 

9- 1/16| 

5-15/16 















































206 


MECHANICAL, DRAFTING. 


Flat-Head Machine Screw 


A| 

1/8 | 

3/16| 

1/4 | 5/16| 3/8 | 7/16| 1/2 | 9/16| 

5/8.| 3/4 

B|40 

|24 

. |20 

|18 |16 1 14 1 12 |12 11 

|10 

r>! 

1/4 | 

3/8 | 15/32J 5/8 | 3/4 | 13/16| 7/8 | 1 | 1- 

-1 8 | 1-3/8 

s| 

. 028| 

.035| 

.051| .057| .064| .081| . 081| .091| 

.114| .128 

X|70 

|70 

170 

|70 |70 |70 [70 |70 |70 

|70 


Round and Fillister Head Machine Screw 


A| 

1/8 | 

3/16| 

1/4 | 

5/16 1 

3/8 | 

7/16| 

1/2 | 9 16| 

5/8 | 3/4 

B|40 

124 

(20 

|18 1 16 

114 |12 |12 |11 |10 

Dl 

3/16] 

1/4 | 

3/8 | 

7/16| 

9/16| 

5/8 | 

3/4 | 13/16) 

7/8 | 1 

s| 

.028| 

.035| 

.0511 

.057| 

.064| 

. 081| 

.081| .091| 

. 114| .128 


Collar-Screw 


A| 

1/8 | 

3/161 

1/4 | 

5/16| 

3/8 | 7/16| 

1,2 | 9/16| 

5/8 | 

3/4 

B|40 |24 |20 

|18 \16 

114 |: 

12 112 [11 |10 


D| 

1/8 | 

3/16| 

1/4 | 

5/161 

3/8 | 7/161 

1/2 | 9/16| 

5/8 | 

3/4 

F| 

11/64| 

17/64| 

11/321 

7/16 : 

17/32| 39/64) 

11/16) 51/641 

7/8 | 1- 

-1/16 

C| 

1/4 | 

11/32 

7/16| 

1/2 | 

5/8 | 11/16) 

15/16| 15/161 

1 1- 

-1/4 

G| 

1/32| 

3/ 641 

1 / 16| 

5/64 1 

3/321 7/ 641 

1/8 ) 9/64) 

5/32) 

3/16 


Pipe Threads 


Diam. 

II 

Thds. Per In. 

1 

Diam. Drill 

II 

Diam. 

Thds. Per In. | 

Diam. Drill 

1/8 

II 

27 

1 

21/64 

II 

1-1/4 | 

11-1/2 | 

1-15/38 

1/4 

II 

18 

1 

29/64 

II 

1-1/2 | 

11-1/2 | 

1-23/32 

3/8 

II 

18 

1 

19/32 

II 

2 

11-1/2 | 

2- 3/16 

1/2 

II 

14 

1 

25/38 

II 

2-1/2 | 

8 ' [ 

2-11/16 

3/4 

II 

14 

1 

15/16 

II 

3 

8 1 

3- 5/16 

1 

II 

11-1/2 

1 

1-3/16 

II 

3-1/2 | 

8 1 

3-13/16 


Standard taper of pipe threads is, 1 inch in 16, or 3/4 inch to 1 foot. 








































RE^RSNCS TABLES. 


207 


U. S. STANDARD SCREW THREADS. 



FORMULA 


p = pitch = 


_ 1 _ 

No, threads per inch 


d = depth = p X .6495 


f = flat = 


P 

8 


Diameter of Screw. 

Threads per Inch. 

Diam. at Root 
of Thread. 

Width of Flat. 


20 

.185 

.0063 


18 

.2403 

.0069 

K 

16 

.2936 

.0078 

& 

14 

.3447 

.0089 

V2 

13 

.4001 

.0096 

16 

12 

.4542 

.0104 

Vs 

11 

.5069 

.0114 

H 

10 

.6201 

.0125 

Vs 

9 

.7307 

.0139 

l 

8 

.8376 

.0156 

IVs 

7 

.9394 

.0179 

1 M 

7 

1.0644 

.0179 

m 

6 

1.1585 

.0208 

iy 2 

6 

1.2835 

.0208 

m 

5 K 

1.3888 

.0227 

IK 

5 

1.4902 

.0250 

m 

5 

1.6152 

.0250 

2 

4 K 

1.7113 

.0278 

2 M 

4/4 

1.9613 

.0278 

2M 

4 

2.1752 

.0313 

2% 

4 

2.4252 

.0313 

3 

334 

2.6288 

.0357 

3M 

334 

2.8788 

.0357 

3K 

334 

3.1003 

.0385 

3M 

3 

3.3170 

.0417 

4 

3 

3.5670 

.0417 

4M 

2 7 A 

3.7982 

.0435 

4 ^ 

2K 

4.0276 

.0455 

4M 

2 y % 

4.2551 

.0476 

5 

2 34 

4.4804 

.0500 

5^ 

234 

4.7304 

.0500 

5 Vo 

2^ 

4.9530 

.0526 

5M 

234 

5.2030 

.0526 

6 

234 

5.4226 

.0556 












208 


MECHANICAL, DRAETlN.G. 


FOR TAPS WITH U. S. STANDARD THREADS. 


Size 

No. 


-Size 

No. 

Size 

Size 

No. 

Size 

Size 

No. 

Size 

of 

of 

Drill. 

of 

of 

of 

of 

of 

of 

of 

of 

of 

Tap. 

Thds- 


Tap. 

Thds. 

Drill. 

Tap. 

Thds 

Drill. 

Tap. 

Thds. 

Drill. 

M 

20 

tk in. 

tt 

11 

2 1 

64 

IV 

7 

l^r 

2 H 

4 y, 

1ft 


18 

C 

% 

10 


iH 

6 

1ft 

2M 

4}4 

1ft 

X 

16 

N 

H 

10 

H 

114 

6 

1ft 

2 Vs 

4 

2* 

& 

14 

S 

Vs 

9 

fi 

IX 

5^ 

1ft 

2Vi 

4 

2& 

X 

13 

ft in. 

it 

9 

ft 

m 

5 

i y 2 




& 

12 

ft in. 

l 

8 

ft 

iVs 

5 

IX 




Vs 

11 

ft in. 

IX 

7 

61 

64 

2 , 

4^ 

ift 





Laying Out Angles with a 2=ft. Rule 

Open a 2-ft rule until the open ends are as far apart as the distance shown in table 
below for the desired angle. To measure an angle reverse the operation. 


Degrees 

Inches 

Degrees 

Inches 

Degrees 

Inches 

1 

1 - 21 

II 

15 

3.12 || 

55 

| 

11.08 

2 

.422 

|| 

20 

4.17 || 

60 

| 

12.0 

3 

.633 

jj 

25 | 

5.21 || 

65 

1 

12.89 

4 

.837 

|| 

30 | 

6.21 || 

70 

| 

13.76 

5 

j 1.04 

II 

35 | 

7.20 |j 

75 

| 

14.61 

7.5 

| 1.57 

|| 

40 | 

8.21 || 

80 

| 

15.43 

10 

2.09 

|| 

45 | 

9.20 || 

85 

| 

16.21 

14.5 

| 3.015 

jj 

50 | 

10.12 || 

90 

| 

16.97 











































reference tables. 


209 


DECIMAL EQUIVALENTS 


Of 8ths 

, 16ths,, 32nds and 64ths 

8ths. 

A = -15625 


.A = .21875 

y% = .125 

A = .28125 

= .250 

M = -34375 

% = .375 

Jf = .40625 

H = -500 

= .46875 

V% = -625 

& = .53125 

H = -750 

= .59375 

Vs = .875 

§i = .65625 


§| = .71875 

16ths. 

§f = .78125 


§J = .84375 

A = .0625 

§ = .90625 

A = -1875 

M = .96875 

A = -3125 


A = -4375 


A = .5625 

64ths. 

U = .6875 


if = .8125 

* = .015625 

if = .9375 

A = .046875 


A = .078125 

32ds.. 

A = -109375 


A = .140625 

A = .03125 

Ji = .171875 

A = .09375 

i} = .203125 

i 


a 


a = 
a - 
a = 
a = 
a = 


a 

a 

a 

a 


.234375 

.265625 

.296875 

.328125 

.359375 

.390625 

.421875 

.453125 

.484375 

.515625 

.546875 

.578125 

.609375 

.640625 

.671875 

.703125 

.734375 

.765625 

.796875 

.828125 

.859375 

.890625 

.921875 

.953125 

.984375 






210 


MECHANICAL DRAFTING. 


WEIGHTS 

OF SQUARE AND ROUND BARS OF CARBON STEEL IN 
POUNDS PER LINEAL FOOT. 


Weight of 1 cubic inch = .285 lbs. 

The following tables are calculated from the unit of 1 cubic 
inch = .3 lbs. which in practice has proved Very accurate as 
nearly all steel is finished slightly full to dimensions. 


Thickness 
or Diameter 
in Inches. 

Weight of 
Square Bar 

One Foot Long. 

Weight of 
Round Bar 

One Foot Long. 

Thickness 
or Diameter 
in Inches. 

Weight of 
Square Bar 

One Foot Long. 

Weight of 

Round Bar 

One Foot Long. 

Thickness 

or Diameter 

in Inches. 

Weight of 

Square Bar 

One Foot Long. 

Weight of 

Round Bar 

One Foot Long. 

ft 

.014 

.011 


11.02 

8.65 

3ft 

42.5 

33.4 

Vs 

.056 

.044 


11.82 

9.28 

3K 

44.1 

34.6 

ft 

.126 

.099 

m 

12.65 

9.94 

3ft 

45.7 

35.8 

H 

.225 

.177 

in 

13.51 

10.61 

3K 

47.3 

37.1 

ft 

.351 

.276 

2 

14.4 

11.3 

3ft 

48.9 

38.4 

Vs 

.506 

.397 

2ft 

15.3 

12.0 

3M 

50.6 

39.7 

T^ 

.689 

.541 

2 K 

16.2 

12.7 

3ft 

52.3 

41.0 

Vl 

.900 

.707 

•2ft 

17.2 

13.5 

3K 

54.0 

42.4 

ft 

1.13 

.895 

2K 

18.2 

14.3 

3ft 

55.8 

43.8 

% 

1.40 

1.10 

2ft 

19.2 

15.1 

4 

57.6 

45.2 


1.70 

1.33 

2K 

20.3 

15.9 

4ft 

59.4 

46.6 

% 

2.02 

1.59 

2ft 

21.4 

16.8 

4 K 

61.2 

48.1 

« 

2.37 

1.86 

2K 

22.5 

17.6 

4ft 

63.1 

49.5 

Vs 

2.75 

2.16 

2 TS 

23.6 

18.52 

4M 

65.0 

51.0 

n 

3.16 

2.48 


24.8 

19.4 

4ft 

66.9 

52.5 

1 

3.60 

2.82 

2ft 

26.0 

20.4 

4K 

68.9 

54.1 

1* 

4.06 

3.19 

2M 

27.2 

21.3 

4ft 

70.9 

55.6 

1 K 

4.55 

3.57 

2 ft 

28.4 

22.3 

4K 

72.9 

57.2 

1* 

5.07 

3.98 

2Vs 

29.7 

23.3 

4ft 

74.9 

58.8 

1 X 

5.62 

4.41 

2n 

31.0 

24.4 

4 Vs 

77.0 

60.4 

1ft 

6.20 

4.87 

3 

32.4 

25.4 

4ft 

79.1 

62.0 

m 

6.80 

5.34 

3* 

33.7 

26.5 

4M 

81.2 

63.7 

ift 

7.43 

5.84 

3K 

35.1 

27.6 

4n 

83.3 

65.4 

ik 

8.10 

6.36 

3ft 

36.5 

28.7' 

4K 

85.5 

67.1 

ift 

8.78 

6.90 

3 K 

38.0 

29.8 

4ft 

87.7 

6».8 

i K 

9.50 

7.46 

3ft 

39.5 

31.0 

5 

90.0 

70.6 

ift 

10.24 

8.05 

3K 

41.0 

32.2 

5ft 

92.3 

72.4 




























of 

>age 

000 

) 00 < 

ooo 

)00l 

ooo 

00 

0 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

21 

22 

23 

24 

25 

26 

27 

28 

29 

30 

31 

32 

33 

34 

35 

36 

37 

38 


REFERENCE TABRES. 


KNESS AND WEIGHT OF SHEET 
STEEL AND IRON. 


Approximate Thickness 

Weight Per Sq. Foot. 

♦Overweight 

Fractions. 

Decimals. 

Steel. 

Iron. 

Up to 

75 in. Wide. 

y> 

.5 

20.320 

20.00 


5 per cent. 

M 

.46875 

19.050 

18.75 


r« 

to 

.4375 

17.780 

17.50 

6 “ “ 

.40625 

16.510 

16.25 


H 

.375 

15.240 

15.00 

y u « 


,34375 

13.970 

13.75 


T fi 

.3125 

12.700 

12.50 

8 “ “ 

A 

.28125 

11.430 

11.25 


17 

.26562 

10.795 

10.625 

Up to 50 in. 

Vi 

.25 

10.160 

10.00 

Wide. 

15 

.23437 

9.525 

9.375 




.21875 

8.890 

8.75 



to • 

.20312 

8.255 

8.125 


7 per cent. 

to 

.1875 

7.620 

7.5 


.17187 

6.985 

6.875 


1 8 y 2 “ “ 

ih 

.15625 

6.350 

6.25 



.14062 

5.715 

.5.625 


1 10 “ “ 

% 

.125 

5.080 

5.00 


> 

A 

.10937 

4.445 

4.375 



.09375 

3.810 

3.75 


& 

.07812 

3.175 

3.125 


xls - 

.07031 

2.857 

2.812 


TS 

.0625 

2.540 

2.50 


tItt 

.05625 

2.286 

2.25 


2 V 

.05 

2.032 

2. 


T60- 

.04375 

1.778 

1.75 


iV 

.0375 

1.524 

1.50 


TTU 

.03437 

1.397 

1.375 


TZ 

.03125 

1.270 

1.25 


9 

■J2(l 

.02812 

1.143 

1.125 



.025 

1.016 

1. 



.02187 

1.389 

.875 


T#t) 

.01875 

.762 

.75 


AV 

.01718 

.698 

.687 


CT 

.01562 

.635 

.623 


ef<T 

.01406 

.571 

.562 



.0125 

.508 

.5 


6lt> 

.01093 

.694 

.437 


1 3 

T2sir • 

.01015 

.413 

.406 


3 2 (7 

.00937 

.381 

.375 


1 1 

T2 

.00859 

.349 

.343 


6i(J 

.00781 

.317 

.312 


Tl/W 

.00703 

.285 

.281 


zVlx) 

.00664 

.271 

.265 


rto 

.00625 

.254 

.25 



211 




















212 


MECHANICAL drafting. 


SIZES OF NUMBERS OF THE U. S. STANDARD GAGE. 


Number 
of Gage. 

Approximate 
Thickness in 
Fractions of 
an Inch. 

Approximate 
Thickness in Decimal 
Parts of an Inch. 

Weight per 
Square Foot 
in Ounces. 
Avoirdupois. 

Weight per 
Square Foot 
in Pounds. 
Avoirdupois. 

16 

A 

.0625 

40 

2.5 

17 

t!^ 

.05625 

36 

2.25 

18 

2 V 

.05 

32 

2. 

19 


.04375 

28 

1.75 

20 

3 

■gff 

.0375 

24 

1.50 

21 

s¥o 

.034375 

22 

1.375 

22 

A 

.03125 

20 

1.25 

23 


.028125 

18 

1.125 

24 

4 V 

.025 

16 

1 . 

25 

sbo 

.021875 

14 

.875 

26 

t! 0 

.01875 

12 

.75 

27 

sV<jr 

.0171875 

11 

.6875 

28 

A 

.015625 

10 

.625 

29 

9 

.0140625 

9 

.5625 

30 

1 

SG 

.0125 

8 

.5 

31 

ff4l) 

.0109375 

7 

.4375 

32 

TS 80 

.01015625 

6 l A 

.40625 

33 

'5%T> 

.009375 

6 

.375 

34 


.00859375 

5 « 

.34375 

35 

sfe 

.0078125 

5 

.3125 

36 

9 

T 2SU 

.00703125 

4^ 

.28125 

37 

zhUo 

.006640625 

4M 

.265625 

38 


.00625 

4 

.25 












REFERENCE tables. 


213 


DIFFERENT STANDARDS FOR WIRE GAGE. 


Number of 
Wire Gage. 

American 
or Brown & 
Sharpe. 

Birmingham 

or 

Stubs’ Wire. 

Washburn & 

Moen Mfg. Co. 

Worcester, Mass. 

Imperial 

Wire Gage. 

Stubs’ 

Steel Wire 

U. S. Standard 

for Plate. 

Number of 

Wire Gage. 

000000 




.464 

- 

46875 

000000 

00000 




.432 


4375 

00000 

0000 

.46 

.454 

.3938 

.400 


.40625 

0000 

000 

.40964 

.425 

.3625 

.372 

.... 

.375 

000 

00 

.3648 

.38 

.3310 

.348 

.... 

.34375 

00 

0 

.32486 

.34 

.3065 

.324 

.... 

.3125 

0 

1 

.2893 

.3 

.2830 

.300 

.227 

.28125 

1 

2 

.25763 

.284 

.2625 

.276 

.219 

.265625 

2 

3 

.22942 

.259 

.2437 

.252 

.212 

.25 

3 

4 

.20431 

.'238 

.2253 

.232 

.207 

.234375 

4 

5 

.18194 

.22 

.2070 

.212 

.204 

.21875 

5 

6 

.16202 

.203 

. 1920 

.192 

.201 

.203125 

6 

7 

.14428 

.18 

.1770 

.176 

.199 

.1875 

7 

8 

.12849 

.165 

.1620 

.160 

.197 

.171875 

8 

9 

.11443 

.148 

.1483 

.144 

.194 

.15625 

9 

10 

.10189 

.134 

.1350 

.128 

.191 

.140625 

10 

11 

.090742 

.12 

.1205 

.116 

.188 

.125 

11 

12 

.080808 

.109 

.1055 

.104 

.185 

.109375 

12 

13 

.071961 

.095 

.0915 

.092 

.182 

.09375 

13 

14 

.064084 

.083 

.0800 

.080 

.180 

.078125 

14 

15 

.057068 

.072 

.0720 

.072 

.178 

.0708125 

15 

16 

.05082 

.065 

.0625 

.064 

.175 

.0625 

16 

17 

.045257 

.058 

.0540 

.056 

.172 

.05625 

17 

18 

.040303 

.049 

.0475 

.048 

.168 

.05 

18 

19 

.03589 

.042 

.0410 

.040 

.164 

.04375 

19 

20 

.031961 

.035 

.0348 

.036 

.161 

.0375 

20 

21 

.028462 

.032 

.03175 

.032 

.157 

.034375 

21 

22 

.025347 

.028 

.0286 

.028 

.155 

.03125 

•22 

23 

.022571 

.025, 

.0258 

.024 

.153 

.028125 

23 

24 

.0201 

.022 

.0230 

.022 

.151 

.025 

24 

25 

.0179 

.02 

.0204 

.020 

.148 

.021875 

25 

26 

.01594 

.018 

.0181 

.018 

.146 

.01875 

26 

27 

.014195 

.016 

.0173 

.0164 

.143 

.0171875 

27 

28 

.012641 

.014 

.0162 

.0149 

.139 

.015625 

28 

29 

.011257 

.013 

.0150 

.0136 

.134 

.0140625 

29 

30 

.010025 

.012 

.0140 

.0124 

.127 

.0125 

30 

31 

.008928 

.01 

.0132 

.0116 

.120 

.0109375 

31 

32 

.00795 

.009 

.0128 

.0108 

.115 

.01015625 

32 

33 

00708 

.008 

.0118 

.0100 

.112 

.009375. 

33 

34 

006304 

.007 

.0104 

.0092 

.110 

.00859375 

34 

35 

005614 

.005 

.0095 

.0084 

.108 

.0078125 

35 

T6 

005 

.004 

.0090 

.0076' 

.106 

.00703125 

36 

O yJ 

004453 



.0068 

.103 

.006640625 

37 

O / 

2Q 

003965 



.0060 

.101 

.00625 

38 

o o 

r\f\ 2 ^ 2 1 



.0052 

.099 


39 

39 

40 

. UU J J A 

.003144 

. 

. 

.0048 

.097 


40 








































214 


MECHANICAL, DRAFTING. 


ABBREVIATIONS 

METALS 


Aluminum . 
Babbitt . 

Brass . 

Bronze . 

Carbon 
Cast brass 
Cast copper 
Cast Iron 
Cast steel . 

Cold rolled steel . 

Copper 

Head 

Malleable iron . 
Open hearth steel 
Phosphor bronze 
Steel 

Steel casting 
Wrought iron 
Zinc 

Tool steel 
Forged tool steel 
High speed steel 


. Almn. 

. Bb. 

B. 

. Bz. 

Cbn. 

. C. B. 

. C. Cop. 

. C. I. 

c. s. 

. C. R. S. 
. Cop. 

. . Head 

M. I. 

. O. H. S. 

Ph. Bz. 

. Steel. 

S. C. 

. W. I. 
Zn. 

. T. S. 

F. T. S. 
. H. S. S. 


GAGES 

Brown & Sharpe, or American Standard 

Wire Gage. 

Birmingham, or Stubs Iron Wire Gage 
National, or Roebling’s, or Washburn & 
Moen’s ....... 

Music Wire Gage .... 

United States Gage .... 

Twist Drill & Steel Wire Gage 
Stubs’ Steel Wire Gage .... 


B. & S. 
B. W. G. 


N. W. G. 
M. W. G. 
U. S. G. 
T. D. G. 
S. W. G. 


FASTENERS 


Button head bolt .... 

Cap screw. 

Double chamfered hexagon nut 

Eye bolt. 

Fillister head brass machine screw 
Fillister head iron machine screw 


Btn. Hd. B. 

Cap Sc. 

Dbl. Chmfd. Hex. Nut. 
Eye B. 

Fil. Hd. B. M. Sc. 

Fil. Hd. I. M. Sc. 












REFERENCE TABLES. 


215 


Flat head wood screw 

Flat Hd. Wd. i 

Flat head stove bolt 

. . . . Flat Hd. Stov< 

Headless set screw . 

. . . . Hdlss. Set Sc. 

Hexagon nut 

. Hex. Nut. 

Lag screw . 

Lag Sc 

Machine bolt 

. . . . Mach. B. 

Machine screw nut . 

M. Sc. Nut. 

Milled body tap bolt 

. M. B. Tap P. 

Set screw . 

Set Sc. 

Square nut 

. Sq. Nut. 

Stud bolt . 

. . . . Stud B. 

T-head bolt . 

. T-Hd. B. 

WEIGHTS AND MEASURES, ETC. 

Center 

Cr. 

Center line 

. C. L. 

Circumference . 

. . . . Circum. 

Diameter 

. dia. or D. 

Foot, feet . 

Ft. or ', e.g.4' 

Horsepower . 

. H.P. 

Inch, inches 

In. or", e.g.4" 


MISCELLANEOUS 

Building 

Bldg. 

Case harden . 

. C.H. 

Company . 

Co. 

Counterbore . 

. Cbr. 

Countersink 

. . . . Csk. 

Cylinder 

. . . . Cyl. 

Drawing 

Dwg. 

General 

. Gnl. 

Hexagon 

Hex. 

Machine 

. Mach. 

Manufacturing 

Mfg. 

Maximum 

. Max. 

Minimum 

. • . . . Min. 

Specification 

. Spec. 

Square 

Sq. 

Standard 

. Std. 

Threads 

Thds. 

Weight .... 

. Wgt. 

Finish 

. . . . /. 













INDEX 


[Numbers Refer to Articles] 


All numbers refer to Articles. 

Angle valves, 77. 

Assembly Drawing, defined, uses, 
characteristics, 74. 

B. 

Babbit, 73. 

Bearings and Hangers, 73. 

Bessemer steel, 97. 

Bessemer nickel, manganese steel, 
97. 

Bevelled Tracing Rule, 41. 
Blueprinting, 120. 

Blueprinting from typewritten sheets, 
127. 

Blueprint solution, 122. 

Blueprint papers, 121. 

Boiler tubes, diameters, 80. 

Bolts and Nuts, 55. 

Bolts and Nuts, process of manu¬ 
facture, 56. 

Bolt and Pipe Dies, 69. 

Border Lines, 3. 

Bore, note for, 51. 

Boring bar, 50. 

Bow Pencil, adjustment, etc., 19. 
Bow Dividers, adjustment, etc., 17. 
Brasses, 73. 

Breaks, conventional, 71. 

Brownprint paper, 123. 

C. 

Cap-screws, 59. 

Ceiling Hanger, 73. 

Chucks, 49. 

Circles in isometric projection, 86. 
Circles in oblique projection, 95. 
Circles in perspective, 116. 

Cleaning Pads, for pens^ 15. 


Cog wheels, pinions, construction of’ 
90. 

Collar screws, 61. 

Compass, adjustment, etc., 35. 

Conventional breaks, 71. 

Conventional lines, 39. 

Construction in perspective, 115. 

Conventional threads, 66. 

Coordinates in perspective, 115. 

Coordinate planes, angles, 28. 

Coupler, for shafting, 72. 

Coupler, for pipe, 81. 

Crucible steel, 97. 

D. 

Detail drawing, defined, 32. 

Detail drawings, order of work, 75. 

Detail drawings, arrangement of de¬ 
tails, 75. 

Detail signature, 32. 

Dies, bolt and pipe, 69. 

Dimensioning, 36. 

Dimensioning, in isometric projec¬ 
tion, 87. 

Dimensioning in oblique projection, 
93. 

Dividers, adjustment, opening, set¬ 
ting, etc., 16. 

Double threads, 68. 

Drop check valves, 79. 

Drawing-board, construction, use. 
Art. 1. 

Drawing paper, quality, position on 
board, etc., 2. 

Drawing pencils, numbering, sharp¬ 
ening, etc., 8. 

Drawing titles, 24. 

Drawing titles, construction, order 
of prominence, etc., 25. 

Drill, note for, 37. 


216 


INDEX. 


217 


E. 

Ellipse, defined, construction, 119. 
Erasers, to clean, 9. 

r. 

Face plate, 49. 

Fillet, how made, 38. 

First, second, third and fourth angle 
projections, 28. 

First angle, elimination, 28. 

Finish, 48. 

Flat-head machine screws, 63. 

Flue hole cutter, use and construc¬ 
tion, 54. 

G. 

Gate valves, 78. 

Gears, construction, 90. 

Globe valves, 77. 

H. 

Hangers, 73. 

Hexagonal and square headed bolts, 
58. 

Horizon in perspective, 112. 
Hydraulic jack, 89. 

X. 

Ink bottles, holders, etc., 21. 
Interpolated sections, 52. 

Iron ores, 97. 

Irregular curve, 35. 

Irregular objects, in isometric pro¬ 
jection, 85. 

Irregular objects in oblique projec¬ 
tion, 96. 

Irregular objects in perspective, 117. 
Isometric projection, definition, prin¬ 
ciples, 82. 

Isometric projection, directrices, 83. 
Isometric axes, 82. 

Isometric projection plane, 82. 
Isometric scale, 84. 

Isorpetric construction, 84. 

Isometric projection, irregular ob¬ 
jects, 85. 


J-K. 

Jacks, 89. 

Keys and keyways, 70. 

Im. 

Lettering pens, 14. 

Letter guide lines, for lettering, par¬ 
allel lines, 18. 

Letter spacing table, 26. 

Lever jack, 89. 

M. 

Machine sketch, defined, 98. 

Machine sketch, nature of, 100. 
Machine sketching, paper for, 99. 
Machine bolts, 57. 

Mechanical letters, width, thickness, 

22 . 

Mill, note for, 51. 

N. 

Name plates, 23. 

Needle points, to make, 6. 

O. 

Objection to globe valves, 77. 

Oblique projective, defined, princi¬ 
ples, 91. 

Oblique axes, etc., 

Oblique scale, 94. 

Oblique construction, 94. 

Offhand letters, components, 11. 
Offhand lettering, heighth and width 
of letters, 10. 

Offhand letters, numerals, height, 
fractions, 13. 

Offhand letters, difficult letters, easy 
style of letter, 12. 

Open hearth steel, 97. 

Order of pencil work on working 
drawings, 34. 

Order of inking in tracing, 40. 

Ores, iron, conversion of, 97. 
Orthographic projections, defined, 27. 
Orthographic projections, principles, 
28. 


218 


INDKX 


Orthographic projections, 28. 

Orthographic projection, summary 
of principles, 29, 

Orthographic projection, permissible 
violations, 30. 

P. 

Paper, for machine sketching, 99. 

Pencil, for sketching, 101. 

Perspective, defined, 106. 

Perspective construction, 114. 

Perspective, principles of construc¬ 
tion, 107. 

Picture plane in perspective, 108. 

Pig iron, 97. 

Pipe coupler, 81. 

Pipe union, flange, 81. 

Pipe union, ground joint, 81. 

Point of sight, position of in per¬ 
spective, 109. 

Point of sight, in perspective, to 
place, 118. 

Positions of third and fourth views, 
47. 

Position of object in perspective, 
108. 

Positive prints on old Vandyke pa¬ 
per, 126. 

Positive printing of typewritten 
sheets, 131. 

Post hanger, 73. 

Principal point in perspective, 110. 

Printing from old blueprints, 128. 

Printing from heavy cardboard, 129. 

Printing from coordinate paper, 130. 

Procedure in sketching, 103. 

Projection of objects, 28. 

R. 

Raised tracing rule, 41. 

Revolved sections, 52. 

Revolution of coordinate planes, 28. 

Round and fillister head machine 
screws, 62. 

Ruling pen, manner of holding, to 
fill, etc., 20. 


S. 

Scale, care, use, 5. 

Scales, architects and engineer’s, de¬ 
fined, 46. 

Scale versus size, 46. 

Scale, architect’s, tables, 42. 

Screws, cap and machine, 59-63. 
Screw jack, 89. 

Second and fourth angles, elimina¬ 
tion, 28. 

Sectioning, 33. 

Sectioning, solid cylinders, 52. 
Section, lines, indication of mate¬ 
rial by, 52. 

Set-screws, 60. 

Shades and shadows, in isometric 
and oblique projection, 88. 

Shaft coupler, 72. 

Shop terms— 

Bore, 51. 

Drill, 37. 

Fillet, 38. 

Finish, 48. 

Mill, 51. 

Tap, 51. 

Short cuts in sketching, 104. 

Size of sketch, 102. 

Sketch pencil, 101. 

Sketch stroke, 101. 

Sketch, size of drawing, 102. 
Sketching, order of procedure, 103. 
Sketching, short cuts, 104. 

Solar paper, 123. 

Square threads, 67. 

Stud bolts, 64. 

Stuffing box, use and construction, 
43. 

Swing check valves, 79. 

T. 

T-Square, 4. 

Tap, 48. 

Tap, note- for, 51. 

Tapping drill, defined, 48. 

Tapping drill, 45. 

Third and fourth views, positions, 
47. 


INDEX. 


219 


Threads, crest, root, outside diame¬ 
ter, root diameter, pitch, 44. 

Threads, shop note, 44. 

Threads, conventional representa¬ 
tion, slope, etc., 44. 

Threads, standard conventions, hid¬ 
den, 53. 

Tool steel, 97. 

Tracing - cloth, preparation of sur¬ 
face, etc., 41. 

Tracing rulers, 41. 

Triangles, to clean, 18. 

Triangles, position on drawing board, 
7. 

U. 

Unit space, 22. 

Unions, ground joint and flange, 81. 

U. S. standard bolt threads, 44. 


V. 

Valves, 76. 

Valve discs and seats, 77. 

Valve bonnets, 77. 

Vandyke, to wash and fix, 124. 
Vandykes, to transparentize, 125. 
Vandyke paper, 123. 

Vanishing points in perspective, 111. 

W. 

Wall hanger. 

Water pipes and boiler tubes, dia¬ 
meters, 80. 

Working drawings, defined, 31. 
Working drawings, positions of third 
and fourth views, 47. 

Wrought iron, 97. 








DEC 14 1912 















































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